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  • 1985-1989  (6,684)
  • 1986  (3,459)
  • 1985  (3,225)
  • Polymer and Materials Science  (6,446)
  • pharmacokinetics  (238)
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Years
  • 1985-1989  (6,684)
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    The intra- and inter-subject variability of Nifedipine pharmacokinetics in young volunteers (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 57-60 
    Details
    ISSN: 1432-1041
    Keywords: nifedipine ; pharmacokinetics ; oral contraceptives ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of Nifedipine were measured following single oral doses of Nifedipine Slow Release (Adalat Retard) on three separate occasions to young, healthy volunteers of both sexes. Intra- and inter-subject variability were assessed by comparing the pharmacokinetic parameters, AUC, Cmax and T50%AUC. Interindividual variability was less than that observed in other studies with the betablockers, metoprolol and propranolol and there was no evidence of differences between the sexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614196
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  • 102
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and pharmacodynamics of the prostacyclin analogue iloprost in man (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 61-68 
    Details
    ISSN: 1432-1041
    Keywords: iloprost ; prostacyclin analogue ; pharmacokinetics ; platelet aggregation ; healthy male volunteers ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels of the prostacyclin analogue, iloprost, were measured by antibody/GC/MS in healthy male volunteers given 1 and 3 ng/kg per min i.v. for 45 min, and 1 µg/kg p.o. Following i.v. infusion, the steady-state plasma levels of iloprost were strictly dose-dependent (46±8 pg/ml and 135±24 pg/ml). The disposition was biphasic with half-lives of 3–4 min and 0.5 h. After oral administration, absorption of the drug was extremely rapid, the maximum plasma level of 251±32 pg/ml being achieved after 10±6 min. The bioavailability was 16±4%. Platelet aggregation induced by 2 µM ADP was reduced by 53% and 68% at the end of the two different infusions, and by 68% 15 min after p.o. administration. The ex-vivo inhibition of platelet aggregation by iloprost was not affected by preceding drug treatment. The cAMP content of platelets was increased by a factor of 2.5 at the end of the infusions and to a lesser extent 15 min after oral dosing. A slight increase in heart rate occurred during the infusion and within 30 min after oral administration; blood pressure was virtually unaffected. Except for transient side-effects (facial flush and headache) no adverse reactions were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614197
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  • 103
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of methysergide and its metabolite methylergometrine in man (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 75-77 
    Details
    ISSN: 1432-1041
    Keywords: methysergide ; methylergometrine ; first-pass metabolism ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy men were given 1.0 mg methysergide maleate intravenously and 2.7 mg methysergide maleate orally in a cross-over study. The systemic availability of methysergide was only 13%, most probably due to a high degree of first-pass metabolism to methylergometrine. We also found evidence of extrahepatic clearance of methysergide. After oral administration the plasma concentrations of the metabolite were considerably higher than those of the parent drug and the area under the plasma concentration curve (AUC) for methylergometrine was more than ten times greater than for methysergide. Our findings may be relevant to the treatment of migraine if methylergometrine contributes to the effect of methysergide. Methylergometrine had a significantly longer elimination half-life than methysergide (223±43 min vs 62.0±8.3 min and 174±35 min vs 44.8±8.1 min in the oral and intravenous studies respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614199
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  • 104
    Electronic Resource
    Electronic Resource
    Effect of cirrhosis and renal failure on the kinetics of clotiazepam (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 89-92 
    Details
    ISSN: 1432-1041
    Keywords: clotiazepam ; liver cirrhosis ; renal insufficiency ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a single 5-mg oral dose of the thienodiazepine clotiazepam was evaluated in a series of patients with biopsy-proven cirrhosis, and in patients with renal insufficiency requiring maintenance hemodialysis, compared to healthy matched controls. Clotiazepam volume of distribution (Vz) was significantly smaller in cirrhotic patients than in controls (1.83 vs 2.57 l/kg), and total clearance was likewise reduced (2.15 vs 3.15 ml/min/kg). Elimination half-life was similar between groups (10.0 vs. 10.2h). There were no significant differences between renal failure and control patients in clotiazepam Vz, oral clearance, or elimination half-life. Thus cirrhosis is associated with reduced clearance of clotiazepam, probably due to impairment of its microsomal oxidation. However clotiazepam disposition is not significantly altered in dialysis-dependent renal insufficiency patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614202
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  • 105
    Electronic Resource
    Electronic Resource
    The effects of age and chronic liver disease on the elimination of temazepam (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 93-97 
    Details
    ISSN: 1432-1041
    Keywords: temazepam ; liver disease ; elimination ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the newer 1, 4 benzodiazepine temazepam were evaluated in 16 healthy subjects aged 18–92 years and in 15 cirrhotic patients, to ascertain the effect of ageing and liver disease. The data were analysed both by classic two compartment and by non-compartmental methods. The mean elimination half-life in the control subjects was 15.5 h, considerably longer than previous estimates. No correlation was found between age and pharmacokinetic parameters. The cirrhotic group showed no statistically significant difference in the pharmacokinetic parameters nor in the urinary recovery of the dose from the control group. Temazepam plasma protein binding was assessed in a second group of 9 cirrhotics of similar severity to the main group and in matched controls. When these binding data were applied to the mean clearance data, a modest although not statistically significant, reduction in free drug clearance was observed in the cirrhotic group. This study adds further support to the observation that drugs which undergo ether glucuronidation have normal elimination patterns in patients with liver disease. Temazepam may prove to be a useful hypnotic sedative in patients with liver disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614203
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  • 106
    Electronic Resource
    Electronic Resource
    Cirrhosis of the liver markedly impairs the elimination of mexiletine (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 83-88 
    Details
    ISSN: 1432-1041
    Keywords: mexiletine ; cirrhosis of the liver ; antiarrhythmic agents ; pharmacokinetics ; intravenous administration ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To study the effects of cirrhosis of the liver on the pharmacokinetics of mexiletine a single i.v. dose of 200 mg was administered to six cirrhotic patients and to six healthy controls. The distribution of mexiletine in both study groups was similar, as indicated by similar values of V1 and Vss, but it tended to occur more slowly in the cirrhotics. The plasma protein binding of mexiletine was unchanged in the patients with cirrhosis. The elimination of mexiletine was markedly retarded in the cirrhotics, as indicated by its lower total clearance (2.31 vs. 8.27 ml/kg/h,) lower total elimination rate constant (0.059 vs 0.353 h−1), and longer elimination half-life (28.7 vs 9.9 h). The antipyrine half-life was 38.3 h in the patients and 14.7 h in the controls. One healthy volunteer had a Morgagni-Stokes-Adams type of syncopal attack 5 min after administration of mexiletine due to disturbance of AV conduction induced by the drug. Thus, on a pharmacokinetic basis the loading dose of mexiletine need not be modified in cirrhotic patients, whereas the maintenance dosage should be reduced to one fourth — one third of the usual dose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614201
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  • 107
    Electronic Resource
    Electronic Resource
    Ceftriaxone pharmacokinetics following multiple intramuscular dosing (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 109-112 
    Details
    ISSN: 1432-1041
    Keywords: ceftriaxone ; intramuscular ; pharmacokinetics ; steady-state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The steady-state pharmacokinetics and tolerance of ceftriaxone after multiple i.m. doses of 0.5 and 1 g q12 h for 3.5 days were investigated in 12 healthy, adult volunteers. Ceftriaxone was rapidly absorbed after i.m. administration with mean peak times ranging from 1.3 to 1.9 h. Steady-state plasma concentrations were apparent after the third dose of both dosage regimens, with trough plasma concentrations of 24±6 and 39±8 µg/ml (mean±SD) after the 0.5 and 1 g q12 h regimens, respectively. Multiple i.m. administrations of ceftriaxone did not alter its elimination half-life; however, small increases were observed in the plasma clearance and volume of distribution at the 1-g regimen. These increases were attributed to the non-linear binding of ceftriaxone to human plasma proteins, and are therapeutically unimportant. Ceftriaxone was well tolerated and serious or lasting adverse reactions were not encountered in the study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614206
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  • 108
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of dezocine, a new analgesic: Effect of dose and route of administration (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 121-123 
    Details
    ISSN: 1432-1041
    Keywords: dezocine ; opioid analgesics ; pharmacokinetics ; healthy volunteers ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intravenous (IV) dezocine, and bioavailability of intramuscular (IM) and subcutaneous (SQ) dezocine, were evaluated in healthy male volunteers. Elimination half-life following 5, 10, and 20 mg IV doses averaged 2.6–2.8 h, and was independent of dose. Clearance decreased slightly, although significantly, with dose. After Deltoid IM injection, dezocine was rapidly absorbed (peak level: 0.6 h after dose), with bioavailability 97%. Thus dezocine has extensive distribution, high clearance and short half-life over a range of IV doses. It is rapidly and completely absorbed following IM or SQ administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614208
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  • 109
    Electronic Resource
    Electronic Resource
    Comparison of single and multiple dose pharmacokinetics of theophylline using stable isotopes (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 113-120 
    Details
    ISSN: 1432-1041
    Keywords: theophylline ; pharmacokinetics ; stable isotopes ; diurnal variation ; single dose administration ; multiple dose administration ; systemic availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Theophylline, enriched with the stable isotopes13C and15N, was administered intravenously in a dose of 10 mg to 8 healthy men following single (200 mg) and multiple (200 mg 8-hourly for 5 days) oral dose administration of aminophylline. Total plasma clearance, volume of distribution, and half-time determined from the intravenous data were similar, demonstrating that the pharmacokinetics of theophylline after chronic dosing can be predicted from the pharmacokinetics of a single dose. With chronic oral dosing, however, the mean trough concentration was 12% higher at 9 a.m. than at 5 p.m., the end of the dose interval (3.94±0.55 vs. 3.50±0.45 µg·ml−1). The AUC following oral dosing was 25% higher in the multiple dose study than in the single dose study. Simulation analysis suggested that these results could be explained by diurnal variation in the clearance or absorption rate or a combination of both. Thus, the systemic availability of theophylline measured during a single dosage interval after chronic oral dosing to steady state would be overestimated in comparison with that measured after a single oral dose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614207
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  • 110
    Electronic Resource
    Electronic Resource
    Single dose oxazepam has no effect on acetaminophen clearance or metabolism (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 127-129 
    Details
    ISSN: 1432-1041
    Keywords: oxazepam ; acetaminophen clearance ; metabolite formation ; glucuronidation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The metabolism of acetaminophen and oxazepam in humans is mainly dependent on the microsomal capacity for glucuronide conjugation. The clearance of acetaminophen and the formation of metabolites were evaluated in 7 patients before and during concomitant administration of oxazepam 30 mg. The subjects received a single 500 mg dose of acetaminophen i.v. and concentrations in plasma were measured for 360 minutes and in urine for 24 h in order to estimate the production of metabolites. The single therapeutic dose of oxazepam had no effect on the clearance of acetaminophen or on formation of its metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614210
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  • 111
    Electronic Resource
    Electronic Resource
    Treatment of essential hypertension with felodipine in combination with a diuretic (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 133-139 
    Details
    ISSN: 1432-1041
    Keywords: felodipine ; hydrochlorothiazide ; essential hypertension ; calcium antagonist ; pharmacokinetics ; plasma noradrenaline ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a double-blind cross-over study, the effect on blood pressure (BP), heart rate (HR) and plasma noradrenaline concentration (pNA) of placebo or felodipine given in addition to hydrochlorothiazide was studied in 12 male patients with essential hypertension, not satisfactorily controlled with the diuretic alone. The first dose of felodipine decreased BP and increased HR for about 6 h. After 4 weeks of treatment with felodipine, BP was reduced for 24 h, whereas HR was only transiently increased. The elimination half-life of felodipine was about 23 h. The plasma noradrenaline concentration increased after felodipine and serum uric acid decreased. Side-effects were few and usually mild.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614290
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  • 112
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and pharmacodynamics in man of the dopamine antagonist ergot derivative, bromerguride (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 165-168 
    Details
    ISSN: 1432-1041
    Keywords: bromerguride ; dopamine antagonist ; pharmacokinetics ; pharmacodynamics ; prolactin level ; side-effects ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma levels and urinary excretion of the dopamine antagonist, bromerguride, were measured by radioimmunoassay in healthy male volunteers given 50 µg i.v. and oral doses of 1 and 2 mg. Plasma prolactin was also measured by radioimmunoassay. Following i.v. injection, the concentration of bromerguride declined biphasically, with half-lives of 7 min and 1.2h. The total clearance was 32 ml·min−1·kg−1 and the apparent volume of distribution was 3.6 l/kg. The bioavailability of oral bromerguride was 29% after 1 mg and 25% after 2 mg. The drug was almost totally metabolized and less than 0.05% of the dose was excreted in urine in 24 h after oral administration. Plasma prolactin levels were increased in a dose-dependent manner for about 8 h. Side-effects were minimal, mainly being tiredness and headache in some of the volunteers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606653
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  • 113
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of tenoxicam in patients with impaired renal function (1986)
    Springer
    European journal of clinical pharmacology 29 (1986), S. 697-701 
    Details
    ISSN: 1432-1041
    Keywords: tenoxicam ; renal insufficiency ; non-steroidal antiinflammatory agents ; protein binding ; metabolism ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of tenoxicam after a single oral dose of 20 mg has been studied in 12 patients with various degrees of decreased renal function. Unchanged tenoxicam and its 5′OH-metabolite in plasma and urine were determined by HPLC. The mean areas under the plasma concentration-time curve (138±53 µg/ml·h) and terminal half-lives in patients with impaired renal function did not differ from values previously reported in normal volunteers, nor did the peak concentration of tenoxicam. The half-life of 5′OH-tenoxicam and unchanged tenoxicam where the same. The urinary excretion of 5′OH-tenoxicam fell with decreasing renal function. Thus no dosage adjustment should be necessary and the usual daily dose of tenoxicam may be administered once daily also to patients with renal failure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615961
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  • 114
    Electronic Resource
    Electronic Resource
    The pharmacokinetics after intravenous and oral administration in man of theα 2-adrenoreceptor antagonist idazoxan (RX781094) (1986)
    Springer
    European journal of clinical pharmacology 29 (1986), S. 743-745 
    Details
    ISSN: 1432-1041
    Keywords: idazoxan ; pharmacokinetics ; alpha 2-adrenoceptor antagonist ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A high performance liquid chromatographic method was developed for the quantitative determination of idazoxan in plasma. The assay was used to study the disposition of the drug after intravenous infusion and oral administration to five normal subjects. After i.v. administration the kinetics could be described by a two compartment model with a mean elimination half life of 4.20 h. The mean calculated volume of distribution during the elimination phase was 3.20 l/kg−1 and the mean plasma clearance was 824 ml min−1. After oral administration a lag period before onset of absorption was observed in all five volunteers, the plasma levels declining monoexponentially from the peak concentration with a mean elimination half life of 5.58 h. The absolute availability varied between 26% and 41% with a mean value of 34%. Invitro measurements produced a blood/plasma ratio of 1.3 for idazoxan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615972
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  • 115
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of temazepam in geriatric patients (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 745-747 
    Details
    ISSN: 1432-1041
    Keywords: temazepam ; pharmacokinetics ; geriatric patients ; benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single dose of temazepam 10 mg, as a solution in soft gelatin capsules, was given to 10 fasting geriatric in-patients (mean age 83 years) in a stable clinical condition. The mean peak plasma concentration was 306 ng/ml, with a median time of 0.75 h to peak concentration. Temazepam was eliminated from plasma in a biexponential manner, with a distribution phase (mean t1/2α=0.7 h) predominating for 3 h. The drug had a mean elimination half-life of 8.7 h. In a chronic study, in which temazepam 10 mg p.o. was given nightly to 13 patients, the plasma concentrations on Days 3, 5, 8, 12 and 15 were not significantly different from each other, showing rapid attainment of steady state levels and the lack of drug accumulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00608229
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  • 116
    Electronic Resource
    Electronic Resource
    5-Aminosalicylic acid in patients with an ileo-rectal anastomosis (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 23-26 
    Details
    ISSN: 1432-1041
    Keywords: sulphasalazine ; Pentasa ; slow release preparation ; 5-aminosalicylic acid ; ileo-rectal anastomosis ; ulcerative colitis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of 5-aminosalicylic acid (5-ASA) from sulphasalazine (SASP) and the slow-release 5-ASA preparation Pentasa was investigated in a cross-over study in 9 otherwise healthy patients with an ileo-rectal anastomosis. The 24-hour recoveries of the drugs were 90.5% and 84.7%, respectively. The median release of 5-ASA from SASP was 50% and from Pentasa 75%. Equal amounts of 5-ASA (18.0% vs 17.9%) were found in the faeces, and a significantly larger amount (4.4% vs 28.9%) of the metaboliteN-acetyl-5-aminosalicylic acid (ac-5-ASA) was found in faeces following Pentasa. A larger amount of 5-ASA was absorbed and subsequently excreted in the urine, mainly as the metabolite (2.5% vs 20.5%) from Pentasa. This confirms previous results in ileostomized patients treated with Pentasa. The present findings also demonstrate that bacterial azo-reduction of SASP in patients with ileorectal anastomosis may be an adequate way to deliver 5-ASA in this type of patient. Both treatments may be used in these patients during a flare up of ulcerative colitis, but randomized studies are needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00870980
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  • 117
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and metabolism of quinidine in extensive and poor metabolisers of sparteine (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 69-72 
    Details
    ISSN: 1432-1041
    Keywords: quinidine ; sparteine ; pharmacokinetics ; drug oxidation ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and metabolism of quinidine were investigated in extensive and poor metabolisers of sparteine. No differences in plasma clearance, terminal half life, volume of distribution or cumulative urinary excretion of quinidine, 3-hydroxyquinidine and quinidine-N-oxide were observed between phenotypes. Thus, it is unlikely that quinidine metabolism is controlled by the sparteine/debrisoquine gene locus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00870989
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  • 118
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of intravenous and intraperitoneal ceftriaxone in chronic ambulatory peritoneal dialysis (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 479-483 
    Details
    ISSN: 1432-1041
    Keywords: ceftriaxone ; dialysis ; continous ambulatory peritoneal dialysis ; pharmacokinetics ; intraperitoneal administration ; intravenous administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of ceftriaxone was investigated in 8 patients without infection, who were receiving continuous ambulatory peritoneal dialysis (CAPD). Ceftriaxone 1 g was injected i.v. and 1 g was given intraperitoneally in the CAPD fluid during a 4-h dwell time. Ceftriaxone was assayed by HPLC. After intravenous administration, the kinetic parameters of ceftriaxone were: plasma t1/2, 12.3 h, total plasma clearance, 14.0 ml/min, volume of distribution at steady state 0.18 l/kg, and peritoneal clearance 0.59 ml/min. Over 72 hours only 5.5% of the dose was eliminated by the peritoneal route. After intraperitoneal administration, ceftriaxone rapidly appeared in serum; the absorption t1/2 was 1.1 h and the mean peak concentration was 38.8 µg/ml. The absorption of ceftriaxone from the peritoneal space was 39%. A single 1.0 g IP dose led to serum and dialysate concentrations of ceftriaxone above the minimum inhibitory concentration for susceptible pathogens for 24 hours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613528
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  • 119
    Electronic Resource
    Electronic Resource
    Diuretic activity, safety and pharmacokinetics of torasemide during chronic treatment in normal subjects (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 1-7 
    Details
    ISSN: 1432-1041
    Keywords: torasemide ; diuretic activity ; pharmacokinetics ; healthy subjects ; side-effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Torasemide 40 mg/day p.o. was administered for 21 days to 8 healthy volunteers to investigate its pharmacodynamics, pharmacokinetics and safety on chronic administration. It induced a highly significant initial increase in 24-h urinary volume and 24-h excretion of sodium and chloride, but its affect diminished after the first days. On Days 0, 1, 10 and 21 the experiement was divided in 3 clearance phases, extending from 0 to 2 h, 2 to 6 h and 6 to 24 h after dosing. The fractional excretion of sodium, chloride, potassium, calcium, magnesium and inorganic phosphates peaked during the first 2 h and returned almost to the control value during the following two clearance phases. The phase-dependent changes were significant for all electrolytes, except for potassium and inorganic phosphate. Plasma electrolyte levels remained constant throughout the study, except for a small decrease in chloride and potassium and for an increase in calcium and magnesium. Fasting blood glucose and glucose tolerance test were unaffected. A small but significant decrease in LDL-cholesterol was observed on Day 10. Other plasma lipid components showed minor changes. Plasma uric acid levels were moderately increased. There was no significant change of the creatinine clearance. Body weight fell significantly (by about 2 kg) during the study. Tonal audiometry was normal before and after the study. There was no significant difference between the plasma levels of torasemide on Days 1, 10 and 21, nor between its elimination half-life on Days 1 and 21. Side-effects consisted mainly of fatigue and low-back pain on days of intense diuresis. There were no toxic symptoms. ECG recordings and blood pressure remained within normal limits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00541460
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  • 120
    Electronic Resource
    Electronic Resource
    Comparative analysis of the pharmacokinetics of unsubstituted N1-derivatives of 1,4-benzodiazepine (1986)
    Springer
    Bulletin of experimental biology and medicine 101 (1986), S. 206-209 
    Details
    ISSN: 1573-8221
    Keywords: 1,4-benzodiazepines ; pharmacokinetics ; plasma/brain concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00836121
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  • 121
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of a water-soluble antioxidant of 3-hydroxypyridine type (1986)
    Springer
    Bulletin of experimental biology and medicine 101 (1986), S. 333-335 
    Details
    ISSN: 1573-8221
    Keywords: antioxidant ; 3-hydroxypyridines ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00835938
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    Radioimmune and radioreceptor study of the pharmacokinetics of the enkephalin analog dalargin in man (1986)
    Springer
    Bulletin of experimental biology and medicine 101 (1986), S. 783-785 
    Details
    ISSN: 1573-8221
    Keywords: dalargin ; pharmacokinetics ; enkephalins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00839605
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  • 123
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    A dispersion model of hepatic elimination: 2. Steady-state considerations-influence of hepatic blood flow, binding within blood, and hepatocellular enzyme activity (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 261-288 
    Details
    ISSN: 1573-8744
    Keywords: hepatic elimination ; hepatic clearance ; availability ; intrinsic clearance ; pharmacokinetics ; dispersion model ; well-stirred model ; tube model ; distributed model ; blood flow ; binding within blood ; hepatocellular enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dispersion model of hepatic elimination is based on the distribution of residence times of blood elements within the liver. The model has two asymptotic solutions corresponding to the “wellstirred” model (complete mixing of blood elements) and the “parallel-tube” model (no variation in residence times of blood elements). The steady-state form of the dispersion model relevant to pharmacokinetic analysis is developed and explored with respect to changes in blood flow, in binding within blood, and in hepatocellular enzyme activity. Literature data are used to evaluate discrepancies among the predictions of the dispersion, well-stirred, and tube models. It is concluded that the dispersion model is consistent-with the data. The limitations of steady-state perfusion experiments to estimate the residence time distribution of blood elements within the liver are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106707
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  • 124
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    In vivo interaction of the enantiomers of disopyramide in human subjects (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 335-356 
    Details
    ISSN: 1573-8744
    Keywords: disopyramide ; pharmacokinetics ; stereoisomers ; antiarrhythmic agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Disopyramide, an antiarrhythmic agent, is marketed as a racemic mixture of two enantiomers. The racemic drug has unusual pharmacokinetic properties because of its concentration-dependent binding to plasma proteins in the therapeutic plasma concentration range. This study examined, in healthy subjects, the individual pharmacokinetic properties of both total and unbound d-and ldisopyramide in plasma after intravenous administration of each enantiomer separately (1.5mg/kg).Also investigated is the pharmacokinetics of total d-and l-disopyramide in plasma after intravenous administration of a pseudoracemate. Both d-and l-disopyramide are found to exhibit concentration-dependent binding to plasma proteins, with d-disopyramide being more avidly bound at lower concentrations. The stereoselective, concentration-dependent binding to plasma proteins resulted in distinct pharmacokinetic properties when the enantiomers were given together as the pseudoracemate. d-Disopyramide had a lower plasma clearance and renal clearance, a longer half-life, and a smaller apparent volume of distribution than l-disopyramide. However, when the enantiomers were administered separately, there were no differences in the clearance, renal clearance, and volume of distribution between enantiomers calculated from either total or unbound drug concentrations. The results reveal an important pharmacokinetic interaction between the enantiomers of disopyramide when given as a racemic mixture, which may be dose-dependent and is not apparent upon administration of the enantiomers separately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059195
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  • 125
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    The impact of neglecting nonlinear plasma-protein binding on disopyramide bioavailability studies (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 365-379 
    Details
    ISSN: 1573-8744
    Keywords: disopyramide ; bioavailability ; protein binding ; nonlinear ; sustained release ; pharmacokinetics ; ultrafiltration ; immunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Disopyramide has nonlinear protein binding and thus the relationship between the extent of its bioavailability and AUC,the area under the plasma concentration-time curve, is (1) nonlinear and (2) absorption rate-dependent. The unbound species follows linear pharmacokinetics. A solution of disopyramide, the innovator's product, and two generic formulations were found to be statistically indistinguishable in their bioavailability of disopyramide, whether comparison was based upon AUCor area under the plasma unbound concentration-time curve (AUCu).The AUCand AUCugave similar results because of truly similar bioavailability, coupled with sufficiently similar release rates, among the four preparations chosen for study. The concentration dependence of disopyramide protein binding and the time course of unbound plasma concentrations were fit by models which then allowed prediction of AUCunder various biopharmaceutical scenarios. Nonlinear binding of disopyramide to plasma proteins renders AUCan insensitive parameter for the discrimination of products with different extents of bioavailability; immediate release products allowing bioavailabilities of 75 or 125% relative to the solution can generate AUCs86 and 112%, respectively, of that from the solution. Nonlinear binding, furthermore, leads to a tendency for AUC tooverestimate the bioavailability of slower release products in single-dose studies; if AUCwere the index of bioavailability, products permitting the same bioavailability as the solution but releasing over 12 hr could appear to allow 114% relative bioavailability. Moreover, in some situations the bias arising from the insensitivity of AUCto product differences can be reinforced by the dependence of AUCon release rate; an apparent relative bioavailability of 80% can be achieved by a 12-hr release product allowing a true relative bioavailability of a mere 58%. While multiple-dose studies appear largely to avoid the tendency to overestimate low bioavailability in slow-release products, in these studies AUCappears to be even more insensitive in resolving discrepancies between products. Assay technology now available makes AUCua feasible and more reliable index of bioavailability than AUCwhen plasma protein binding of drugs is nonlinear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059197
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  • 126
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    On the pharmacokinetics of 16-acetyl-gitoxin and its bioavailability from pengitoxin-containing tablet formulations (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 357-364 
    Details
    ISSN: 1573-8744
    Keywords: 16-acetyi-gitoxin ; pengitoxin ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In six volunteers the pharmacokinetics of 16-acetyI-gitoxin (16AG, 0.5mg) administered intravenously (A1) and as an oral solution (A2) and of pengitoxin (PAG, 0.6 mg) administered intravenously (A3) was evaluated. In six volunteers the bioavailability of 16AG from two PAG tablet formulations (1.2 mg) (B2, B3) was measured by comparison with the absorption after administration of a pengitoxin solution (1.2mg) (B1). In both studies the test was performed using a crossover design. After a single i.v. injection of equimolar doses, 16AG and PAG showed similar mean kinetic parameters: t 1/2 =51.6hr (16AG) and 60.8 hr (PAG), CL=11.7ml min−1 (16AG) and 12.7ml min−1 (PAG), CLR=4.1 ml min−1 (16AG) and 4.2ml min−1 (PAG). The 16AG was absorbed from solution with a mean half-life of 0.2hr to an extent of 98.6%. The mean urinary excretion /Ae(0, 4)/ of 16AG amounted to 24.6% (A1), 20.8% (A2) and 28.1% (A3). On the basis of AUCvalues, the mean bioavailability of PAG from either tablet formulation amounted to 79.6% (B2) and 89.6% (B3). The pharmacokinetic parameters of 16AG (PAG) are closer to those of digitoxin than those of digoxin. In general, 16AG is characterized as a digitoxin with a digoxin-like elimination half-life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059196
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  • 127
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    Pharmacokinetics of isosorbide dinitrate and its mononitrate metabolites after intravenous infusion (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 1-17 
    Details
    ISSN: 1573-8744
    Keywords: isosorbide dinitratekw]isosorbide 2-mononitrate ; isosorbide 5-mononitrate ; metabolism ; pharmacokinetics ; modeling ; simultaneous estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Plasma concentrations of isosorbide dinitrate (ISDN) and its two active metabolites 2-isosorbide mononitrate (2-ISMN) and 5-isosorbide mononitrate (5-ISMN) have been measured during and for 6 hr after intravenous infusion at a rate of 2.5mg/hr during 1.75 hr in six cardiac patients, by a capillary gas chromatographic method. Data were analyzed by simultaneous modeling of the observed kinetics of the three compounds. Two or three phases were detected on the postinfusion ISDN concentration-time curves. ISDN concentrations declined with a mean terminal half-life of 2.81 hr±0.7 SD. The mean systemic clearance of ISDN (2.9 L/min ±0.7 SD) and its mean total volume of distribution (259 L +- 48 SD) were relatively high. Plasma 5-ISMN concentrations were 5- to 6-fold greater than those of 2-ISMN during the whole observation period. Maximum levels of 2-ISMN (6.7 ng/ml ± 0.9 SD) and of 5-ISMN (27 ng/ml ± 6 SD) occurred within a few minutes after the end of infusion. The mean half-lives of 2-ISMN (1.59 hr± 0.19 SD) and of 5-ISMN (3.78 hr± 0.79 SD) estimated by the model were smaller than those calculated by a model-independent method (2.95 hr± 0.41 SD and 5.98 hr± 2.22, respectively), but were in good agreement with those reported in the literature following separate administration of both metabolites to man. This study shows how such modeling can distinguish between metabolite formation and elimination processes and allow the determination of metabolite half-lives after administration of the precursor drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059280
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    Physiological pharmacokinetic modeling ofcis-dichlorodiammineplatinum(II) (DDP) in several species (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 131-155 
    Details
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; physiological model ; cisplatin ; DDP ; cis-dichlorodiammineplatinum(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A physiological pharmacokinetic analysis ofcis-dichlorodiammineplatinum(II) (DDP) is presented for the rabbit, dog, and human. The results are compared to a previous analysis for the rat. DDP binds irreversibly to low-molecular weight nucleophiles and macromolecules to form mobile and fixed metabolites at rates which are tissue-specific. The rate constant for the formation of fixed metabolite in plasma, determined by in vitro incubation, ranges from 0.004 to 0.008 min−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065258
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    Receptor-mediated model relating anticonvulsant effect to brain levels of camazepam in the presence of its active metabolites (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 309-321 
    Details
    ISSN: 1573-8744
    Keywords: camazepam ; temazepam ; oxazepam ; pharmacokinetics ; anticonvulsant effect ; radioreceptor assay ; rat ; mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In a displacement test using3H-diazepam as a radioligand, the in vitro affinities of metabolites of camazepam (CZ) for the benzodiazepine receptors were 1–50 times more potent than that of CZ. In contrast, only three metabolites (temazepam, oxazepam, and hydroxy CZ), as well as CZ itself, exhibited an in vivo affinity parallel to their ability to protect against pentylenetetrazole-induced clonic convulsion in rats. In addition, CZ and these active metabolites displaced the radioligand from their receptor sites in a concentration-dependent saturable manner, indicating the competitive bimolecular interaction of these molecules with their receptors. The percent anticonvulsant effect was a nonlinear, single-valued function of the in vivo percent displacement of specific3H-diazepam binding, independent of these displacers after i.v. dosing; this relationship could be approximated by the Hill equation. On the basis of these findings, a receptor-mediated model, including the Langmuir equation to describe the receptor binding-brain concentration relationship and the Hill equation to accommodate the anticonvulsant effect-receptor binding relationship, was constructed. This model was found to adequately relate the time course values of anticonvulsant effect and of brain levels of CZ and its active metabolites after oral administration. These results demonstrate that CZ and its active metabolites exert anticonvulsant effect by competitive binding to the benzodiazepine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106709
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    Effect of caffeine on ceftriaxone disposition and plasma protein binding in the rat (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 397-408 
    Details
    ISSN: 1573-8744
    Keywords: caffeine ; ceftriaxone ; plasma ; tissue ; pharmacokinetics ; compartment model ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previous studies have shown that caffeine can affect drug kinetics by altering drug binding to plasma protein, drug absorption, or drug distribution. In this study, the effect of caffeine on the in vivoprotein binding and the disposition of ceftriaxone (a highly protein-bound cephalosporin) were investigated in the rat. Ceftriaxone 100mg/kg and caffeine 20mg/kg were i.v. injected via the tail vein and ceftriaxone in plasma, plasma filtrate, urine, feces, and tissues (brain, heart, kidney, liver, gut, lung, and muscle) was assayed by HPLC with UV detection. The fraction of free ceftriaxone in plasma ranged from 5.6 to 32.8% of total ceftriaxone (3–347 μg/ml) without caffeine and showed no alteration by caffeine. The total amount of ceftriaxone excreted in urine and feces was increased significantly (p〈0.05)from 13.1±1.8mg (mean±SD, 54.6% of total) to 15.3 ±1.1 mg (63.8% of total) by caffeine coadministration. The terminal half-life of ceftriaxone in plasma was shortened from 59 to 47 min, and the area under the plasma drug concentration-time curve (AUC)was reduced from 612 to 516 μg hr/ml Although the peak drug concentrations and the times of peak concentration of ceftriaxone in tissues were not altered by caffeine administration, the elimination of ceftriaxone was increased, as indicated by generally shorter half-lives (decreases ranged from 17.5% in liver to 34.2% in brain) and lower AUCvalues (from 9.0% in heart to 54.5% in brain). These results suggest that caffeine does not alter the protein binding of ceftriaxone, but enhances the elimination of ceftriaxone in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059199
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    Drug pharmacokinetics and the carbon dioxide breath test (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 29-49 
    Details
    ISSN: 1573-8744
    Keywords: carbon dioxide ; breath test ; pharmacokinetics ; metabolite ; extraction ratio ; aminopyrine ; caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interrelationship of the pharmacokinetics of a drug and the expiration of carbon dioxide formed as a metabolite have been studied. The pharmacokinetic characteristics of the drug that affect the usefulness of the carbon dioxide excretion as a measure of liver function were examined by means of computer simulations. The parent drug extraction ratio, fraction demethylated, volume of distribution, and absorption rate of an oral dosage form all contribute to the carbon dioxide breath test result. A drug that would be a useful substrate when the carbon dioxide breath test is used as a probe for changes in liver function should be at least 50% metabolized by demethylation, have a hepatic extraction ratio of 0.2–0.5, and be administered in a form that is rapidly absorbed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059282
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  • 132
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    Effects of the rate and composition of fluid replacement on the pharmacokinetics and pharmacodynamics of intravenous furosemide (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 495-509 
    Details
    ISSN: 1573-8744
    Keywords: furosemide ; pharmacokinetics ; pharmacodynamics ; fluid replacement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Effects of differences in the rate and composition of intravenous fluid replacement for urine loss on the pharmacokinetics and pharmacodynamics of furosemide were evaluated using the dog as a model animal. Each of six dogs received 8-hr constant intravenous infusion of 20 mg (15 mg used in one dog) of furosemide with 0% replacement (treatment I), 50% replacement (treatment II), and 100% replacement (treatment III) with lactated Ringer's solution, as well as with 100% replacement with 5% dextrose in water (treatment IV). Most pharmacokinetic parameters, such as plasma clearance, steady-state volume of distribution, mean residence time, and terminal half-life, were essentially the same in all four treatments. Renal clearances and urinary excretion rates of the drug in treatments II–IVwere essentially the same, but about 20% higher than those in treatment I.In spite of the similarities in kinetic properties, diuretic and/or natriuretic effects from furosemide were markedly different among the four treatments. For example, mean 10-hr urine outputs were 646, 1046, 3156, and 1976 ml and mean 10-hr sodium excretions were 87.0, 142, 383, and 97.2 mmole for treatments I–IV,respectively. Except for treatment III,diuresis and/or natriuresis were found to be time-dependent, generally decreasing with time until reaching a low plateau during later hours of infusion. The present findings also showed that (1)no fluid replacement and 100% replacement with 5% dextrose solution both produced the same degree of severe acute tolerance in natriuresis, indicating the insignificance of water compensation in tolerance development; (2)in treatment II,where neutral sodium balance was achieved, the development of acute tolerance in diuresis and natriuresis can mainly be attributed to negative water balance under this special condition; (3)at steady state the hourly diuresis and natriuresis could differ up to about ten times between treatments. Some implications for the kinetic/dynamic relationship or modeling, in the clinical use, and in the bioequivalence evaluation of dosage forms are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059657
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    Amiodarone pharmacokinetics. I. Acute dose-dependent disposition studies in rats (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 601-613 
    Details
    ISSN: 1573-8744
    Keywords: amiodarone ; pharmacokinetics ; dose-dependent ; rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Single intravenous bolus doses of amiodarone hydrochloride of 30, 60, 90 and 120 mg/kg were administered to male Sprague-Dawley rats to determine the effects of dose on amiodarone pharmacokinetics. Serial blood samples and total urine were collected over 48 hr and assayed for amiodarone and desethylamiodarone by HPLC. The blood amiodarone concentration-time curves for the four doses were best described by a triexponential equation with terminal half-lives (t 1/2γ ) ranging from 17 to 20 hr. Over the dose range studied, no changes in γ, t 1/2γ , or central compartment volume (Vc=1.2–1.4 L/kg) were observed. On the other hand, reductions in amiodarone clearance (CL and steady-state volume of distribution (V ss of 44% (17.7 to 10.0 ml/min per kg) and 50% (16.4 to 8.2 L/kg), respectively, were noted as the dose of amiodarone increased. The conversion of amiodarone to desethylamiodarone (fm was dose-independent and amounted to approximately 10% of each amiodarone dose. No amiodarone or desethylamiodarone was detected in the urine of any of the treated animals. The blood-to-plasma concentration ratio of amiodarone was concentration-independent and therefore did not account for the dose-dependent changes in Vss and CL observed. The data suggested that the dose-dependent changes noted were due to an alteration in the volume (s) of the peripheral tissue compartment(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067966
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    Analysis of pethidine disposition in the pregnant rat by means of a physiological flow model (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 381-395 
    Details
    ISSN: 1573-8744
    Keywords: pethidine ; rat ; physiological flow model ; pharmacokinetics ; pregnancy ; scale up ; opiates, GC-MS analytical method ; simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The disposition of pethidine (meperidine) in the pregnant rat is described by means of a physiological flow model. The model includes arterial and venous blood, brain, fat, fetal, hepatic, intestinal, muscular, pulmonar, and renal tissues. The concentration-time profiles of pethidine calculated by the model are consistent with experimental data, except for the brain and renal tissues, where the model predicts initially higher concentrations. Simulations are carried out to further explore the contribution from different organs on the kinetics in blood and tissues. The tissue-to-blood partition coefficients vary over a range from 5 to 316, where fat has the lowest and liver the highest after a correction is made due to hepatic extraction. Rapid uptake occurs into highly perfused organs such as brain, kidneys, liver, and lungs, followed by fetus, intestines, muscle, and fat. Data indicate no marked membrane resistance to pethidine of the investigated organs, except for fetal tissues, but rather a perfusion-limited uptake. Simulations suggest that muscles and adipose tissue play an important role in the rat, becoming the major reservoir of drug during the intermediate and terminal elimination phase, respectively. Volume of distribution and the biological half-life agree with reported findings. Pethidine is subject to a high systemic blood clearance, which exceeds the total hepatic blood flow in the rat. No degradation of pethidine is found in blood, and therefore a pulmonary expression for pethidine clearance is added as a potential source of pethidine elimination. The elimination of pethidine after a single i.v. bolus dose is found to be dependent on simulated changes in cardiac output and hepatic blood flow. A simulation is performed with the scaled model to mimic the human concentration-time profiles in maternal blood and brain tissues and fetal tissue during repetitive doses of pethidine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059198
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    Saturable Processes Affecting Renal Clearance of Cefixime in Dogs (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 150-155 
    Details
    ISSN: 1573-904X
    Keywords: renal clearance ; cephalosporin ; cefixime ; tubular reabsorption ; saturable protein binding ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of cefixime, a new orally active cephalosporin, was studied after an intravenous dose of 50 mg/kg to four beagle dogs. Cefixime was shown to exhibit concentration dependent serum protein binding and saturable tubular reabsorption. The drug was excreted mainly in the urine, the net result of glomerular filtration and saturable tubular reabsorption. The experimental results were analyzed by model independent pharmacokinetic equations and with theoretical models describing renal clearance. Modification of the models, based on observed data, was proposed. The experimental methods employed and the pharmacokinetic approach offered in this study can be applied to drugs that exhibit concentration dependent protein binding and saturable renal elimination processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016309923717
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    The Effect of Amiodarone on Theophylline Pharmacokinetics in the Rat (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 167-169 
    Details
    ISSN: 1573-904X
    Keywords: amiodarone ; theophylline ; pharmacokinetics ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amiodarone is an investigational antiarrhythmic agent which has been implicated in reducing the activity of the hepatic mixed-function oxidase system. To evaluate this effect further, two groups of six male Sprague–Dawley rats each received theophylline (6 mg/kg, iv) preceded by either normal saline or amiodarone HC1 (100 mg/kg, iv). Blood samples were obtained serially for a period of 6 hr and the sera were assayed for theophylline by high-pressure liquid chromatography (HPLC). In rats pretreated with amiodarone, a significant 45% reduction in the mean (± SD) systemic clearance [0.057 (0.010) vs 0.031 (0.004) liter/hr/kg, P 〈 0.001] and a greater than 100% increase in the mean elimination half-life [2.03 (0.46) vs 4.29 (0.71) hr, P 〈 0.001] of theophylline were observed. These data demonstrate an acute inhibitory effect of amiodarone on the hepatic microsomal enzyme system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016366008696
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    Engineering Targeted In Vivo Drug Delivery. I. The Physiological and Physicochemical Principles Governing Opportunities and Limitations (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 333-344 
    Details
    ISSN: 1573-904X
    Keywords: drug delivery, targeted ; prodrugs ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A physiologically based model is presented to aid prediction of the pharmacological benefits to be derived from the administration of a drug as a targeted drug–carrier combination. An improvement in the therapeutic index and an increase in the therapeutic availability are the primary benefits sought. A measure of the former is obtained from the value of the drug targeting index, a newly derived parameter. Both the drug targeting index and the therapeutic availability are directly calculable. The minimum information needed for approximating both parameters is the candidate drug's total-body clearance and some knowledge of the target site's anatomy and blood flow. Drugs with high total-body clearance values that are known to act at target tissues having effective blood flows that are small relative to the blood flow to the normal eliminating organs will benefit most from combination with an efficient, targeted carrier. Direct elimination of the drug at the target site or at the tissue where toxicity originates dramatically improves the drug targeting index value. The fraction of drug actually released from the carrier at both target and nontarget sites can radically affect index values. In some cases a 1% change in the fraction of the dose delivered to the target can result in a 50% change in the drug targeting index value. It is argued that most drugs already developed have a low potential to benefit from combination with a drug carrier. The approach allows one to distinguish clearly those drugs that can benefit from combination with targeted in vivo drug carriers from those drugs that cannot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016332023234
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  • 138
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    Influence of Malnutrition on the Disposition of Metronidazole in Rats (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 352-355 
    Details
    ISSN: 1573-904X
    Keywords: malnutrition ; metronidazole ; pharmacokinetics ; rats ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of dietary protein deficiency on the disposition of metronidazole and its two major metabolites was examined in male Sprague–Dawley rats fed for 4 weeks on a 23% (control-) or a 5% (low-) protein diet ad libitum. Following an intravenous bolus dose of 10 mg/kg metronidazole hydrochloride, blood samples were obtained serially for a period of 24 hr after drug administration. Serum concentration–time data were analyzed by nonlinear least-squares regression, as well as noncompartmental techniques. The average mean residence time (MRT) was significantly prolonged by 48%, while the systemic clearance (Cl) was decreased by 42% in the protein-deficient rats. Since there was no alteration in the apparent steady-state volume of distribution (V ss), the mean harmonic half-life was increased from 2.9 to 5.0 hr in the protein-deficient rats. Although the percentage of metronidazole recovered as total drug in the urine over 24 hr was not significantly different between the two groups of animals, rats on a low-protein diet excreted a significantly smaller percentage of the administered dose as unchanged metronidazole (mean ± SD, 24.6 ± 3.8 vs 36.5 ± 12%) and a larger percentage (16.7 ± 2.6 vs 8.3 ± 1.8%) as the hydroxylated metabolite. No significant difference in the partial metabolic clearance of the hydroxylated metabolite of metronidazole was seen between the two groups of animals; however, there was a significant decrease in the renal clearance of metronidazole (1.45 ± 0.68 vs 0.55 ± 0.06 ml/min/kg) in the rats fed a low-protein diet. We conclude that the decreased clearance of metronidazole in protein deficiency is a result primarily of the decreased glomerular filtration rate, decreased biliary excretion, and/or increased net tubular reabsorption of metronidazole.
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    URL: http://dx.doi.org/10.1023/A:1016433724142
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  • 139
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    Bioavailability of Propranolol After Oral, Sublingual, and Intranasal Administration (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 108-111 
    Details
    ISSN: 1573-904X
    Keywords: propranolol ; intranasal ; sublingual ; absorption ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of propranolol was compared after oral, sublingual, and intranasal administration in eight healthy male volunteers. Relative to the bioavailability after intranasal (in) administration, which was previously shown to be nearly complete (F relin = 100%), the sublingual (sl) administration of a standard 10-mg tablet gave a bioavailability of F relsl = 63 ± 22%, while the oral (or) administration yielded only F relor = 25 ± 8%. The serum concentration–time curves of propranolol after sublingual administration resembled those of a sustained-release preparation. This sustained-release phenomenon after the sublingual route is reflected in the mean residence times (MRTs) of propranolol in the body (MRTor = 5.7 ± 1.3 hr, MRTsl - 6.4 ± 1.3 hr, MRTin = 4.6 ± 1.0 hr; mean ± SD; N = 8). MRTs after sublingual administration were significantly longer than after the oral and the intranasal doses (P 〈 0.05 and P 〈 0.002, respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016345504153
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  • 140
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    Pharmacokinetics and Reversible Biotransformation of Sulfinpyrazone and Its Metabolites in Rabbits. I. Single-Dose Study (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 173-177 
    Details
    ISSN: 1573-904X
    Keywords: sulfinpyrazone ; pharmacokinetics ; reversible metabolism ; single dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In rabbits receiving sulfmpyrazone (SO) and the sulfide metabolite (S) in four separate experiments, the biotransformation of SO into S was found to be reversible, which resulted in approximately parallel terminal disposition profiles for the three major substances in plasma, i.e., SO, S, and the p-OH-sulfide (OH-S). However, differences in disposition kinetics were observed between the intravenous and the peroral administration. The formation of OH-S was independent of both the administered compound and the administration route. The results obtained in the present studies, the previously documented enterohepatic recirculation, and the formation of S by hindgut flora may have implications for studies on sulfinpyrazone, which has been used as an antithrombotic agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016370209604
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  • 141
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    Pharmacokinetics and Reversible Biotransformation of Sulfinpyrazone and Its Metabolites in Rabbits. II. Multiple-Dose Study (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 178-183 
    Details
    ISSN: 1573-904X
    Keywords: sulfinpyrazone ; pharmacokinetics ; reversible metabolism ; multiple dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In crossover studies rabbits were given sulfmpyrazone (SO) and its sulfide metabolite (S) perorally once daily (10 mg/kg) for 5 days. Comparison of the pharmacokinetic parameters obtained after the first and the fifth dose indicates that repeated dosing does not alter disposition kinetics of both SO and S, except that in dosing with S the observed terminal half-life for S is significantly reduced, from 4.59 ± 0.55 to 2.86 ± 0.6 hr (SD). In other studies rabbits were given higher single doses (15, 25, and 50 mg/kg) perorally and comparison was made between these dose sizes and the first dose (10 mg/kg) of multiple administration with S. Some kinetic parameters tended to be altered in a nonlinear fashion, and greater intersubject variations were observed because of the dose increase, while oxidation to SO or p-hydroxylation to OH-S from S was not significantly altered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016322326443
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  • 142
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    Pharmacoclinical data on high dose medroxyprogesterone acetate in advanced breast cancer (1986)
    Springer
    Breast cancer research and treatment 8 (1986), S. 161-163 
    Details
    ISSN: 1573-7217
    Keywords: medroxyprogesterone acetate ; pharmacokinetics ; response ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01807705
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  • 143
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    α-Helical oligopeptides with hydrophobic side chains soluble in lipophilic solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1-4 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250102
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  • 144
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    Conformations of dinucleoside monophosphates in relation to duplex DNA structures (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 17-30 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mononucleotide conformations are important in understanding the structural aspects of nucleic acids and polynucleotides. In order to study the influence of stacking interactions between adjacent bases in a polynucleotide on the preferred conformations of mononucleotides, conformational energy calculations have been carried out on dinucleoside monophosphate fragments. Four base sequences - d(ApT), d(TpA), d(CpG), and d(GpC) -  have been analyzed in the framework of helical structures. Flexibility of the furanose ring has been incorporated in the investigations. Energetically favored conformers of the four compounds correspond to a variety of left- and right-handed uniform helical structures, similar to those of the commonly observed polymorphous forms. Implications of these investigations on the further understanding of double-helical polynucleotide conformations are briefly discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250104
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  • 145
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    Vibrational circular dichroism of polypeptides, V. A study of 310-helical-octapeptides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 79-89 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured vibrational CD spectra in the 3600-1250 cm-1 region of two monodisperse, protected octapeptides, which form right-handed 310-helices in CDC13 solution. The spectra are similar in sign pattern to those obtained for right-handed α-helices in solution but are smaller in magnitude and, additionally, provide evidence of some line-shape differences. The delineation of this type of ordered conformation was accomplished by means of 1H-nmr. Such a solution structure is consistent with the x-ray crystal structure of one of these molecules.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250107
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  • 146
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    Interaction of calcium ions with gastrin fragments of increasing chain length (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 135-152 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of a series of biologically active gastrin fragments with calcium ions has been investigated by CD in trifluoroethanol. It was found that the gastrin octapeptide pGlu10,Nle15-HG[10-17] binds one calcium ion per molecule. The hypothesis is made that the binding involves the C-terminal, biologically important tetrapeptide. When the chain is elongated to the gastrin nonamer pGlu9,Nle15-HG[9-17], a second binding site is available, which is most likely situated at the N-terminal part of the molecule. Further elongation of the peptide chain up to the dodecapeptide pGlu6,Nle15-HG[6-17] does not provide any additional binding site. Saturation of the two sites in the shorter peptides produces different changes in the chiroptical properties in the near- and far-uv. As the chain is elongated, this difference tends to disappear. This result is consistent with an increased conformational order of the longer peptides. In the shorter fragments, the strength of this second binding is appreciably lower than that of the first, while in the longer peptides, the strength of the two bindings is comparable. On the assumption that the variation of the CD properties is proportional to the extent of binding, the constant for the binding of the second ion was determined to be of the order of 5 × 105 L/mol for the nonapeptide.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250110
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  • 147
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250201
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  • 148
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    UV-induced reduction of Cu(II) in DNA complex studied by Cu-K-edge XANES (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 217-221 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250202
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  • 149
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    Conformational properties of gastrin peptides: Synthesis, biological activity, and preliminary CD characterization of the (Asp)5 analog of des-Trp1, Leu12-minigastrin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 229-234 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250204
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  • 150
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    A molecular mechanical study of netropsin-DNA interactions (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 249-266 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present molecular mechanical calculations on the complexes of netropsin with dA6·dT6, d(TATATA)2, d(CGCGCG)2, and d(CGCGAATTCGCG)2. The complexes were model built using computer graphics and then completely energy refined. Our calculations are consistent with the observed AT preference for netropsin and suggest that mixed sugar pucker geometries should be more stable than uniform in netropsin complexes with poly[d(A-T)]·poly[d(A-T)] and poly(dA)·poly(dt). The netropsin·d(TATATA) and netropsin·dA6·dT6 complexes are significantly different in structure, leading to a possible reason why the observed thermodynamics of netropsin-association with poly[d(A-T)]·poly[d(A-T)] and with poly(dA)·poly(dT) are so different. We also model built and energy refined a structure of netropsin-d(CGCGAATTCGCG)2 using as a guide the nmr data of Patel [(1982) Proc. Natl. Acad. Sci. USA, 79, 6424-6428] and found a three-dimensional structure qualitatively consistent with the NOE enhancements observed by him. After our calculations were completed, we learned of an x-ray structure of a netropsin:d(CGCGAATTCGCG)2 complex, and we compared the structure found in our calculation with the x-ray structure.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250207
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  • 151
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    Dependence of oxygen quenching of intercalated methylene blue triplet lifetime on DNA base-pair composition (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 307-316 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We utilize the dynamic quenching of the triplet state of methylene blue by molecular oxygen to observe changes in the rate at which oxygen can penetrate the helix as a function of base-pair composition. The results indicate that the interior of the oligonucleotide dA-dT is more accessible than dG-dC to small molecules such as dioxygen.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250211
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  • 152
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250301
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  • 153
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    Spermine-nucleic acid interactions: A theoretical study (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 375-392 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of spermine with nucleic acids is simulated theoretically using refined semi-empirical energy formulae and an advanced minimization procedure. Various nucleic acids are considered: model homopolymeric DNA's, a dodecamer (CGCGAATTCGCG) of type B-DNA, as well as a transfer RNA, tRNAPhe. The dominant role of electrostatic potential in determining the preferential binding sites of spermine is demonstrated in each of these cases and the role of counterions, nucleic acid structure, and base-pair sequence is analyzed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250302
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  • 154
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    Temperature dependence of dielectric constant at 10 GHz of Na-DNA gels (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 241-247 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Permittivity ε′ and dielectric loss ε″ of aqueous Na-DNA gels have been measured at 10 GHz in the temperature interval -15 to + 45°C. The experimental results are analyzed in terms of a three-component equation (Na-DNA, interfacial water, bulk water) and yield a value of 35 water molecules/nucleotide interacting with DNA. According to theoretical and experimental data the presence of strongly bonded and weakly bonded water is considered. The modified water exhibits a mean dielectric relaxation time two-or threefold greater than that of bulk water.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250206
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  • 155
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    The effect of solvent viscosity and temperature on DNA viscoelastic behavior (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 291-306 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of solvent viscosity (ηs) and temperature (T) on the shape of the concentration dependence of the principal and total recoils in creep-recovery viscoelastometry experiments has been studied for T4 DNA solutions. The range of DNA concentration (c) was 2 - 40 μg/ml; glycerol, 70-80% v/v, sucrose, 60% v/v; NaCl, 5 mM - 1M; and T, 275 - 323 K. A linear proportionality between recoil and c was obtained at high ηs/T. At low ηs/T, the c-dependence was nonlinear, approaching saturation at higher c. At low c, the slope of both curves was the same. Transition between “linear” and “nonlinear” values occurred over a narrow range of ηs/T (a width of 1-5 K if ηs/T was changed by varying T). (ηs/T)tr, the midpoint of the transition, was independent of solvent properties other than viscosity. Also, (ηs/T)tr increased with c. For a given c, ηs/T values above this transitional value yield linear behavior; below this, nonlinear behavior. The ratio of linear to nonlinear recoil values is a linear function of c with Kc, the slope of this dependence, independent of ηs and T. A kinetic model for the observed nonlinearity of recoil with c is presented. It explains the independence of Kc on ηs and T. An attempt has been made to explain the linear-nonlinear transitions by comparison of τ1 and TR, the lifetime of the contact points of the polymer network in the de Gennes theory. The nonlinear values are consistent with a pseudogel that exists when τ1 〈 TR. At τ1 〉 TR, the DNA behavior is similar to that in dilute solutions (linear values). Thus, the condition for transition is τ1 = TR. However, some unsolved problems remain.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250210
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  • 156
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    The growth of large single crystals of lysozyme (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 337-350 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If protein single crystals larger than those suitable for x-ray analysis are obtained, various spectroscopic, thermal, mechanical, and electrical measurements become possible. To understand the factors governing the crystal size, tetragonal lysozyme crystals were grown in batches at 15°C from solutions of different protein and salt concentrations between pH 4-7. The number and size of the crystals, and the protein concentration remaining in the supernatant, varied markedly with the initial salt amount, pH, and cation species, but large crystals always grew when the initial protein concentration (P) was in a narrow range of 2.5-3 times the crystal solubility (S). It was also shown (1) that the period before the first crystals appeared (D) varied as D ∝ (P/S)-n, where n ≃ 5, and (2) that many previous experiments used more supersaturated solutions than the optimal ones thus determined. The reason why large crystals grow only from moderately supersaturated solutions is discussed. The crystal size of the orthorhombic form grown at 40°C was less sensitive to pH and P than the tetragonal form. An effort to measure D and the solubility at 40°C revealed many differences between the two crystal forms, which we ascribe to different interactions to promote crystallization.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250213
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  • 157
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    Conformational changes of pinellin in solution using intrinsic fluorescence and CD as probes (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 393-405 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pinellin is a plant protein extracted from the rhizome of the Chinese herb Pinellia. It has the ability to abort early pregnancy in mice as well as in rabbits. Studies on the conformational changes of pinellin have been carried out in our laboratory using intrinsic fluorescence and CD. Experimental results show that some tryptophanyl side chains are buried more deeply than others, which results in the heterogeneity of tryptophanyl emission. CD data indicated a high content of β-pleated sheet and β-turn for the backbone conformation. The results of fluorescence and CD measurements both demonstrated the presence of intermediates along the path of denaturation. The following was proposed as the unfolding mechanism of pinellin in 6M guanidine hydrochloride: native state → first intermediate → second intermediate → fully unfolded state.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250303
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  • 158
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    Examination of the secondary structure of proteins by deconvolved FTIR spectra (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 469-487 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourier transform ir (FTIR) spectra of 21 globular proteins have been obtained at 2 cm-1 resolution from 1600 to 1700 cm-1 in deuterium oxide solution. Fourier self-deconvolution was applied to all spectra, revealing that the amide I band of each protein except casein consists of six to nine components. The components are observed at 11 well-defined frequencies, although all proteins do not exhibit components at every characteristic frequency. The root mean square (RMS) deviation of 124 individual values from the 11 average characteristic frequencies is 1.9 cm-1. The observed components are assigned to helical segments, extended beta-segments, unordered segments, and turns. Segments with similar structures do not necessarily exhibit band components with identical frequencies. For instance, the lower frequency beta-structure band can vary within a range of approximately 15 cm-1. The relative areas of the individual components of the deconvolved spectra were determined by a Gauss-Newton, iterative curve-fitting procedure that assumed Gaussian band envelopes for the deconvolved components. The measured areas were used to estimate the percentage of helix and beta-structure for each of 21 globular proteins. The results are in good general agreement with values derived from x-ray data by Levitt and Greer. The RMS deviation between 22 values (alpha- and beta-content of 11 beta-rich proteins measured by both techniques) is 2.5 percentage points; the maximum absolute deviation is 4 percentage points.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250307
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  • 159
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    Fluorescence decay of ethidium bromide in the presence of the Z-conformation of poly-(dG-dC) and of poly(dG-dC) modified by chlorodiethylenetriamine platinum(II) chloride (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 507-518 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A time-resolved fluorescence study of ethidium bromide (EB) in the presence of poly(dG-dC) and of poly(dG-dC) modified by chlorodiethylenetriamine platinum(II) chloride is presented under solvent conditions in which these polymers adopt the Z-conformation (high ionic strength). It is shown that these polynucleotides can intercalate a very small quantity of EB. The binding parameters have been determined. The fluorescence lifetime of EB is slightly higher when bound to the Z-conformation (≃25 ns) than when bound to the B-conformation (≃23.7 ns). The nature of the salt has been checked. In the presence of 2.5M NaClO4, no transition from the Z-conformation to another conformation is observed when EB is added. On the contrary, in the presence of 4.25M NaCl, EB induces a cooperative transition from the Z-conformation to a conformation characterized by a much higher affinity for EB intercalation. In the case of poly(dG-dC) this last conformation is identical to the one observed at low ionic strength (B-conformation), but in the case of the platinated polymer this conformation is slightly different, as judged by the smaller value of the fluorescence lifetime of the intercalated EB.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250309
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  • 160
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    DNA orientation during gel electrophoresis and its relation to electrophoretic mobility (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 539-554 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensities of polarized fluorescence from ethidium bound to phage λ DNA undergoing agarose gel electrophoresis were measured. The intensities were strongly field dependent at voltage gradients of 8 V/cm, consistent with a partial orientation of DNA helices in the direction of electrophoresis about 500 times larger than seen in the same field in solution. Such an orientation was predicted by a reptation model of gel electrophoresis advanced by Lumpkin et al. [(1985) Biopolymers, 24, 1573-1593]. The present results can be fit successfully to this theory with a single adjustable parameter, the gel-DNA contact distance. Also, λ DNA electrophoretic mobilities in the same concentration gel were determined using the same buffer system. Both orientation and mobility measurements can be fit to the reptation theory within a factor of two using the same values of two parameters, the gel-DNA contact distance and the ratio of DNA charge to frictional coefficient.
    Additional Material: 5 Ill.
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    Effect of NaCl on the association of thrombin with heparin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 527-537 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The association of heparin with thrombin was investigated by fluorometric titration. A maximum of 25% of the fluorescence of fluorescein-labeled heparin (FTC-heparin) was quenched at thrombin saturation in the absence of NaCl. FTC-heparin (H) associated tightly with thrombin (T) and the association constant of the ternary complex, H2T, formed in the absence of NaCl, was calculated to be 1.7 × 108M-1. However, the association was strongly influenced by the NaCl concentration, and the association constant of the equimolar complex, HT, formed in 0.15M NaCl was found to be 1 × 106M-1. The first-order rate constant, kapp, for inactivation of thrombin by antithrombin III (AT III) and low-affinity heparin (LA-heparin) was comparable with that of high-affinity heparin (HA-heparin) in the absence of NaCl, but decreased with an increase in the concentration of NaCl. The decreased enhancement of the thrombin-AT III reaction by LA-heparin at high NaCl concentration appeared to result from a decreased association of thrombin with LA-heparin, thus reducing the formation of the ternary complex, thrombin-LA-heparin-AT III.
    Additional Material: 4 Ill.
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    Structural studies of poly(α-aminoisobutyric acid) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 607-625 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-diffraction pattern of an oriented film of poly(α-aminoisobutyric acid) in the 310-helical conformation has been analyzed. The conformation was obtained by a linked-atom least-squares refinement of average values from crystal structures. Specimens treated with dichloracetic acid, to improve their crystallinity, conform to space group R3c with a = 21.8 Å, c = 5.95 Å. The structure contains channels that can accommodate molecules of dichloracetic acid. One molecule of acid per six residues fills the channels, and the R-factor then is 34% using 23 reflections. Ir evidence is presented to show that the acid may hydrogen bond to the peptide groups. Some reflections occasionally observed on the diffraction photographs are attributed to a 15/4 α-helix. The significance of the results is considered in relation to Aib-containing peptides.
    Additional Material: 7 Ill.
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    The relationship of bound water to the IR amide I bandwidth of albumin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 639-654 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four different types of ir experiments, involving changes in pH, changes in pressure, and the use of nonaqueous solvents, and with either albumin molecules dissolved in saline or adsorbed albumin films, support the hypothesis that the bandwidth of the amide I vibration of albumin is directly related to the amount of bound water in this protein. From the amide I band narrowing and the amide I shift to higher frequencies, it is proposed that a more ordered helix structure results as the amount of bound water is decreased.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250409
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    Sequence-dependent recognition of DNA duplexes: Netropsin complexation to the TATA site of the d(G-G-T-A-T-A-C-C) duplex in aqueous solution (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 707-727 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have recorded one-dimensional exchangeable proton and two-dimensional nonexchangeable proton nmr spectra on the complex of netropsin with the self-complementary d(G-G-T-A-T-A-C-C) duplex in aqueous solution between 25° and 35°C. The antibiotic amide, pyrrole, and methylene protons, and the nucleic acid base and sugar H1′, H2′, H2″, and H3′ protons, have been assigned from an analysis of the two-dimensional nuclear Overhauser effect (NOESY) spectra of the complex. We observe intermolecular NOEs between the antibiotic concave face amide, pyrrole, and CH2 resonances, and the adenosine H2 and sugar H1′ protons of base-pairs T3·A6 and A4·T5 in the central TATA core of the d(G1-G2-T3-A4-T5-A6-C7-C8) duplex. We present a molecular model outlining these seven antibiotic-DNA contacts for the complex in solution. The observed line-broadening of several base and sugar protons at the TATA minor groove netropsin binding site in the complex at 35°C are interpreted in terms of intermediate exchange between two orientations of bound netropsin on the duplex.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250413
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    Influence of different tripeptides on the stability of the collagen triple helix. I. Analysis of the collagen sequence and identification of typical tripeptides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1069-1080 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amino acid sequence of the collagen α1(I) chain (calf) is analyzed. Deviations of random tripeptide distribution leads to the definition of clusters. Inside these regions, collagen-typical tripeptides are located. Besides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp, the polar sequences Gly-Glu-Hyp, Gly-Ala-Arg, Gly-Glu-Arg, and Gly-Pro-Lys form typical sequences. The neighborhood of each tripeptide is analyzed and classified. The proximity to the collagen-typical tripeptides is registered. Cluster theory: Less-typical sequences also fold as members of the collagen triple helix and they are as reasonable as well as important for the collagen structure as the cluster tripeptides, but only the latter are important for the nucleation of the triple-helical folding.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250607
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    Peptide-bond distortions and the curvature of α-helices (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1087-1093 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent accessible peptide bonds in proteins exhibit a 1-3° compression of the OCN bond angle and a corresponding expansion of the NCCa bond angle, relative to buried peptide bonds. These changes are consistent with an increase in hydrogen bonding to the carbonyl oxygen accompanying solvent exposure (J. D. Dunitz and F. K. Winkler, (1975) Acta Cryst. B31, 251-263). For amphiphilic structures such as α-helices, systematic differences in peptide-bond geometry between solvent-exposed and buried residues will generate significant curvature. A decrease of 4° in the OCN bond angle between hydrophilic and hydrophobic sides of an amphiphilic helix will lead to smooth bending, with a radius of curvature of about 70 Å. This curvature is in the range observed for α-helices in proteins. Helix curvature is estimated to have only a small effect on the magnitude and direction of the helical dipole moment.
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    URL: http://dx.doi.org/10.1002/bip.360250609
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    SANS studies of concentrated protein solutions. I. Bovine serum albumin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1157-1175 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small-angle neutron scattering (SANS) was used to examine concentrated bovine serum albumin solutions of up to 20% protein w/v. At higher protein concentrations, scattering data show distinct features that can be ascribed to strong intermolecular interactions. Differential scattering cross-sections are fitted to a theoretical model of interparticle potential consisting of a hard core plus an exponentially decaying “tail.” For moderate ionic strength (0.03M K Acetate, pH 5.9), the intermolecular interaction agrees with the double-layer repulsive part of the well-known DLVO (Derjaguin, Landau, Verwey, Overbeek) theory for interacting colloidal particles. We thus demonstrate that it is possible to determine size parameters and the surface charge of protein molecules in dense solutions. At high salt concentrations (≥0.2M NaCl) data can be fitted by the same potential model, although interpretation in terms of DLVO theory is not possible. Even in this case, however, “effective” molecular size and potential parameters can be determined.
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    Diffusion of DNA in a gel under an intermittent electric field (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1179-1184 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250702
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  • 169
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    Shape complementarity at the hemoglobin α1β1 subunit interface (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1229-1247 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational method for attempting to predict protein complexes from the coordinates of the individual proteins has been developed. It is based on matching complementary patterns of knobs and holes. The computer algorithm correctly and uniquely predicts the association of the alpha and beta subunits to form the αβ dimer corresponding to the α1β1 interface in the hemoglobin tetramer. It fails to correctly dock trypsin inhibitor onto trypsin. Nevertheless, this lone success is still a significant advance over previous protein-docking algorithms. The method is also important because it introduces several ways to measure the shape of protein surface regions.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250705
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    Enantioselective interactions of inversion-labile trigonal iron(II) complexes upon binding to DNA (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1209-1228 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the interactions of the substitution-inert inversion-labile complexes Fe(bipy)32+ and Fe(phen)32+ [and the inversion-stable complex Ru(bipy)32+] with DNA. The association of these complexes to DNA is mainly electrostatic, and Fe(phen)32+ shows a more effective binding to DNA than the two bipyridyl complexes, possibly owing to a different binding mode. The interactions are enantioselective, leading to a Pfeiffer shift in the diastereomeric inversion equilibria and an excess of the Δ-enantiomer of Fe(phen)32+ and Fe(bipy)32+, which is directly monitorable through CD. The partition constants for the inversion equilibrium range from 1.3 to 2.0 for Fe(bipy)32+ and Fe(phen)32+, depending on ionic conditions. From flow LD information about the orientation of the complexes on DNA was obtained: it is consistent with a fit of the Δ-enantiomer in the major groove of the right-handed DNA helix. The mechanisms of interaction are discussed against equilibrium, spectroscopic, and kinetic data.
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    URL: http://dx.doi.org/10.1002/bip.360250704
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    Distribution of Mn2+ ions around poly(rI)·poly(rC) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1283-1297 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution of bound Mn2+ ions about poly(rI)·poly(rC) has been studied by measuring the effect of this paramagnetic metal ion on the relaxation behavior of poly(rI)·poly(rC) protons. By combining selective spin - lattice and spin - spin relaxation rates for various protons, some of the principle regions of ion association can be identified. The relaxation data on the CH6 proton are consistent with a 〈 10% occupancy of phosphate inner-sphere binding sites. The broadening of the imino proton resonance requires a substantial occupancy of sites located in the major groove, possibly near IN7. This would also be consistent with the observation that IH8 resonance is the proton most susceptible to relaxation by Mn2+. The relaxation data for the IH2 proton indicate a relatively low occupancy of minor-groove binding sites (e.g., IN3).
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    URL: http://dx.doi.org/10.1002/bip.360250709
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    Adsorption of thionine on heparin studied by combining ultrafiltration and difference VIS spectroscopyThis paper is dedicated to Prof. Georg Manecke on the occasion of his 70th birthday. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1273-1281 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combination of ultrafiltration and difference spectroscopy allows the quantitative determination of spectra of thionine bound to heparin. The spectra of the bound dye do not depend on the degree of coverage; this and the shape of the Scatchard plot show that “all-or-none” binding is valid. A calculus of variations based on a modification of the Hill plot shows that aggregates of seven thionine cations are bound. Tetrasaccharides with an average charge of two carboxylate and five sulfate groups are suggested to be the binding sites. The binding constant given for one mole thionine is 4.4 · 105 M-1. The Gibbs enthalpy for binding of one mole of thionine is -31.7 kJ·M-1 at 20°C.
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    URL: http://dx.doi.org/10.1002/bip.360250708
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    Kinetics of ethidium's intercalation in packaged bacteriophage T7 DNA: Effects of DNA packing density (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1345-1357 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of ethidium's intercalative binding to DNA packaged in bacteriophage T7 and two T7 deletion mutants have been determined, using enhancement of fluorescence to quantitate binding. At a constant ethidium concentration, the results can be described as first-order binding with two different rate constants, k1* (= k1 + k-1) and k2* (= k2 + k-2). The larger rate constant (k1*) was at least four orders of magnitude smaller than the comparable first-order forward rate constant for binding to DNA released from its capsid. At 25°C values of k1* decreased as the amount of DNA packaged per internal volume increased. This latter observation indicates that the rate of ethidium's binding to packaged T7 DNA is limited by an event that occurs inside of the DNA-containing region of T7, not by the crossing of T7 capsid's outer shell. Arrhenius plots of kM1* are biphasic, indicating a transition for packaged DNA at a temperature of 20°C. The data indicate that k1* s are limited by either sieving of ethidium during its passage through the packaged DNA or subsequent hindered intercalation.
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250801
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    Molecular structure of the cis-syn photodimer of d(TpT) (cyanoethyl ester) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1399-1417 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three-dimensional structure was determined by x-ray crystallography for d(T[p](CE)T), a uv photoproduct of the cyanoethyl (CE) derivative of d(TpT), having the cis-syn cyclobutane (CB) geometry and the S-configuration at the chiral phosphorus atom. The crystals of C23H30N5O12P · 2H2O belong to the orthorhombic space group P212121 (Z = 4), with cell dimensions a = 11.596 Å, b = 14.834 Å, and c = 15.946 Å, containing two water molecules per asymmetric unit. The CB ring is puckered with a dihedral angle of 151°. The two pyrimidine bases are rotated by -29° from the position of direct overlap of their corresponding atoms. This represents a major distortion of DNA, since in DNA adjacent thymines are rotated by +36°. The pyrimidine rings are puckered with Cremer-Pople parameters for T[p] and in parentheses [p]T: Q: 0.24 Å (0.31 Å); θ: 123° (120°); φ: 141° (86°). These represent half-chairs designated as 6H1 (T[p]) and 6H5 ([p]T). The CB and pyrimidine ring conformations are interrelated, and we postulate that they execute a coupled interconversion in solution. The T[p] segment has the syn glycosyl conformation, a 2T3 sugar pucker, and gauche- conformation at C4′-C5′; the [p]T segment is anti, 3T4, trans. The C5′-O5′ torsion of the [p]T unit is -124.5°, and the C3′-O3′ torsion of the T[p] unit is -152.9°. Bond angles and bond lengths involving the phosphorus atom are similar to those of other phosphotriesters. The P-O3′ and P-05′ torsion angles are -138.1° and 58.6°, respectively. Several intermolecular (but no intramolecular) hydrogen bonds are found in the crystal.
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    Conformation of mucous glycoproteins in aqueous solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1505-1517 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light-scattering techniques have been used to measure the z-average radius of gyration Rg z-average translational diffusion coefficient Dt and weight-average molecular weight Mw of porcine submaxillary mucin (PSM) in solution. PSM isolated at low shear in the presence of protease inhibitors has a Mw about twice as large as a sample prepared without these precautions. The former sample has a Mw of 17 × 106 in 0.1M NaCl, which decreases to 8 × 106 in 6M guanidine hydrochloride (GdnHCl) and then to 2 × 106 on addition of 0.1M mercaptoethanol to the 6M GdnHCl solution. The Rg or D-1t values obtained for PSM in this work superimpose with those of other authors for different mucin glycoproteins, leading to linear log-log relationships to the molecular weight of the protein core. Comparison of these results with those in the literature for denatured proteins suggest that mucins are linear random coils in which the protein core is stiffened by the presence of the oligosaccharide side chains. The length of the oligosaccharides and the nature of the solvent have little effect on the extension of the protein core. This suggests that the stiffness of the protein core is maintained by steric repulsion of the residues at the beginning of the oligosaccharide chains.
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    URL: http://dx.doi.org/10.1002/bip.360250809
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    Conformation and aggregation of melittin: Effect of pH and concentration of sodium dodecyl sulfate (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1493-1504 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of melittin, a surface-active polypeptide, in solution was studied by CD spectra between 190 and 240 nm. The molecule was essentially unordered (possibly with a trace of helix) in water without salt at neutral pH. Upon deprotonation of four of the six cationic groups at pH 12 the polypeptide became partially helical (about 35%). The addition of NaDodSO4 to an aqueous melittin solution first caused the solution to become turbid but it became clear again in excess surfactant solution. The conformational changes depended on the molar NaDodSO4/melittin ratio, R. With R from 2.34 to 23.4, the melittin solution was turbid and the polypeptide conformation was probably a mixture of α-helix and β-sheets. This was supported by the ir spectrum of the turbid solution, which indicated the presence of both conformations. With R = 46.8 or 468 (1 or 10 mM NaDodSO4) the polypeptide conformation was characteristic of an α-helix, about 70-80% of the molecule, regardless of whether the surfactant was above or below its critical micelle concentration. This compared well with the x-ray results of 92% helix in crystals. The lower helicity of melittin in NaDodSO4 solution might be attributed to the end effects that destabilize the first and last turn of an helix at its N- and C-terminus, respectively.
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    URL: http://dx.doi.org/10.1002/bip.360250808
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    Evolutionary similarity among peptide segments is a basis for prediction of protein folding (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1565-1577 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short segments of polypeptide, from a protein for which the primary sequence but not the three-dimensional structure is known, are compared to a library of known structures. The basis of comparison is the probability with which residues in the unknown segment might substitute through evolution for residues in segments of known structure. In test cases, segments from known structures that are similar in sequence to those from a protein treated as unknown are often found to be similar in three-dimensional structure to one another and to the true structure of the “unknown” segment. This provides a basis for prediction of the local configuration (secondary structure) of polypeptides.
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    URL: http://dx.doi.org/10.1002/bip.360250813
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  • 179
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    Can the double helix be parallel? (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1603-1606 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250903
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    The crystal structure of the photosynthetic inhibitors DCMU and DTPU (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1615-1621 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction studies have been carried out on a single crystal of the photosynthetic inhibitors N-(3,4-dichlorophenyl)-N′-dimethylurea (DCMU) and its newly synthesized spin-labeled analog N-(3,4-dichlorophenyl)-N′-(3,3,5,5-tetramethylpiperidine-4-oxyl)-urea (DTPU). The synthesis of DTPU as well as its crystallographic data are reported. The crystal system of both compounds is monoclinic with a space group P21/c. The cell constants of DCMU are a = 7.759(1), b = 14.737(3), c = 9.233(2) Å, β = 100.99(6)°; of DTPU they are a = 6.976(1), b = 11.998(2), c = 23.585(3) Å, β = 91.38(5)°. Comparison of conformational parameters of DCMU and DTPU reveal differences in the dihedral angle between the aromatic ring and the ureido plane. The measured volumes of DCMU and DTPU are 259.1 and 493.3 Å3, respectively. These figures suggest the size of the binding site of the inhibitors in the photosynthetic membrane.
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    URL: http://dx.doi.org/10.1002/bip.360250905
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    Stereochemistry of peptides containing 1-aminocyclopentanecarboxylic acid (Acc5): Solution and solid-state conformations of Boc-Acc5-Acc5-NHMe (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1635-1644 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a β-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III β-turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The φ,ψ values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (φ≃ ± 60°, ψ∼ ±30°).
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250907
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  • 182
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    Rate constants and activation parameters for the mobility of bulk and DNA-associated glycol-water solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1685-1695 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decrease in mobility of viscous glycol-water solvents when associated with native DNA is quantified from a study of the loss of the exciting-wavelength dependence of the phosphorescence spectrum of free and bound proflavin with increasing temperature. The data are interpreted in terms of a distribution of rate constants with an Arrhenius temperature dependence. Over the temperature range of the experiments a relative decrease of ∼ 104 in the average rate constant is observed for reorientation of the solvent when associated with DNA. The basis for this large reduction is found to derive from a large decrease in the pre-exponential factors (i.e., activation entropy) associated with the reorientation rate constants. The changes in the distribution of rate constants and the activation parameters for solvent mobility induced by DNA do not resemble the changes observed for any one of a number of small ion or molecule perturbations. The results suggest the presence of disorganized, relatively immobile solvent in association with DNA.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250911
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  • 183
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    Calculations on the effect of methylation on the electrostatic stability of the B- and Z-conformers of DNA (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1697-1715 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three-dimensional Poisson-Boltzmann equation for the distribution of counterion charge density around double-helical DNA has been solved for solutions of .01M, .10M, and .20M monovalent salt. The polymers, poly[d(CpGp)] and poly[d(m5CpGp)], were studied in the B- and the Z-conformations. The effect of methylation on the relative stabilities of these conformers in solutions of different ionic strengths is known to favor the Z-form. Accumulation of charge density around the B- and the Z-conformers is compared in detail. The relative electrostatic stabilities of the B- and Z-conformers in .01M, .10M, and .20M solutions are compared and discussed in terms of the ion-DNA interactions and the self-energy of the structured ionic environment. The ion-DNA interaction energies, termed “phosphate screening,” monotonically decrease with ionic strength and are consistent with a B-to-Z conformation change induced in either polymer by increased electrolyte concentration. However, these calculated energies alone do not account for the fact that the ionic strength at the midpoint of the transition of the methylated polymer is substantially lower than that of its unmethylated analogues. The phosphate screening effect is counterbalanced by changes in the self-energy required for the creation of the structured counterion environment. This self-energy of the electrolyte environment monotonically increases with ionic strength. Methylation-induced shifts in the overall conformational equilibria depend on the relative changes of these competing effects. Increasing salt concentration is calcualted to favor the Z-conformer. The effect of methylation, lowering the ionic strength of the transition midpoint, is proposed to originate in minor structural changes in the Z-form of the polymer, making the groove more accessible to counterions in the G(3′ - 5′)C region. This allows a redistribution of counterion density and a lowering of the self-energy of the ionic environment, conferring added stability to the Z-conformation, as indicated by calculations of relative entropies. The experimentally observed temperature dependence of the B-to-Z transition, however, cannot be explained without assuming the release of bound water. Maps of the calculated three-dimensional structure at the counterion distribution near the surface of these molecules in both the B- and the Z-forms are also presented.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250912
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  • 184
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    Vibrational circular dichroism spectra of three conformationally distinct states and an unordered state of poly(L-lysine) in deuterated aqueous solution (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1751-1765 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourier transform ir vibrational circular dichroism (VCD) spectra in the amide I′ region of poly(L-lysine) in D2O solutions have confirmed the existence of three distinct conformational states and an unordered conformational state in this homopolypeptide. Characteristic VCD spectra are presented for the right-handed α-helix, the antiparallel β-sheet, an extended helix conformation previously referred to as the so-called “random coil,” and a completely unordered conformation characterized by the absence of any amide I′ VCD. VCD for the antiparallel β-sheet in solution and the unordered chain conformation are presented for the first time. Each of the four different VCD spectra is unique in appearance and lends weight to the view that VCD has the potential to become a sensitive new probe of the secondary structure of proteins in solution.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250915
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  • 185
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    The hinge-bending mode of a lysozyme-inhibitor complexSupported in part by a grant from the National Institutes of Health. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1767-1802 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hinge-bending mode of hen egg white lysozyme is studied by a constrained minimization technique. Results with and without a bound inhibitor, tri-N-acetyl-glucosamine, are obtained. The frequency of the mode with the inhibitor is found to be 4.3 cm-1, in contrast to 3.0 cm-1 for the free enzyme. Also, the hinge-bending angle with the lowest energy is shifted 10° towards a more closed cleft in the bound species. The main contribution to these differences arise from interactions with the residues lining the cleft and those on the back side of it. Structural details that account for the energetics are presented. The method of calculation is somewhat different from a previous study [J. A. McCammon, B. R. Gelin, M. Karplus & P. G. Wolynes, (1976) Nature 262, 325-326] to reduce the likelihood of artifacts in the results.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250916
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  • 186
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    Pf1 virus particle dynamics (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1859-1864 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The overall dynamics of the Pf1 filamentous bacteriophage particle in solution are characterized by nmr experiments. The chemical-shift anisotropy powder-pattern lineshapes from both DNA and protein backbone sites of the virus are motionally averaged in the same way, indicating that the entire particle undergoes rapid (〈 104 Hz) reorientation about the long axis of the filament when the virus is in solution at high pH. In contrast, the virus particles in samples at low pH are immobile on this time scale.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251004
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  • 187
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    Structure and internal mobility of proteins: A molecular dynamics study of hen egg white lysozymeSupported in part by a grant from the National Institutes of Health. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1909-1937 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and internal motions of the protein hen egg white lysozyme are studied by analysis of simulation and experimental data. A molecular dynamics simulation and an energy minimization of the protein in vacuum have been made and the results compared with high-resolution structures and temperature factors of hen egg white lysozyme in two different crystal forms and of the homologous protein human lysozyme. The structures obtained from molecular dynamics and energy minimization have root-mean-square deviations for backbone atoms of 2.3 Å and 1.1-1.3 Å, respectively, relative to the crystal structures; the different crystal structures have root-mean-square deviations of 0.73-0.81 Å for the backbone atoms. In comparing the backbone dihedral angles, the difference between the dynamics and the crystal structure on which it is based is the same as that between any two crystal structures. The internal fluctuations of atomic positions calculated from the molecular dynamics trajectory agree well with the temperature factors from the three structures. Simulation and crystal results both show that there are large motions for residues involved in exposed turns of the backbone chain, relatively smaller motions for residues involved in the middle of helices or β-sheet structures, and relatively small motions of residues near disulfide bridges. Also, both the simulation and crystal data show that side-chain atoms have larger fluctuations than main-chain atoms. Moreover, the regions that have large deviations among the x-ray crystal structures, which indicates flexibility, are found to have large fluctuations in the simulation.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251008
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  • 188
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    The interaction of Ca2+-binding proteins with the carbocyanine dye stains-allThis study was supported by NIH Grant AM 30322-04. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1579-1595 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of the carbocyanine dye Stains-all with the Ca2+-binding proteins calmodulin, troponin C, and parvalbumin has been monitored by means of absorption spectra and CD. In the absence of Ca2+, complexes with Stains-all of all three proteins exhibit at high dye: protein mole ratios an intense J absorption band at 600-650 nm, which is associated with a characteristic CD spectrum. In the cases of calmodulin and troponin C, the J-band is progressively lost as the dye: protein ratio decreases and is replaced by bands of the γ and β types at 450-550 nm, which likewise give rise to characteristic CD spectra. For parvalbumin, only the J-band is observed; its intensity is undiminished at the lowest dye: protein ratios examined. In the presence of excess Ca2+ the J-band is lost for all three proteins. For calmodulin and troponin C it is replaced by σ- and β-bands; in the case of parvalbumin the bound dye is released. A tentative model has been proposed to account for these observations.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250814
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  • 189
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    Prediction of the native conformation of a polypeptide by a statistical-mechanical procedure. II. average backbone structure of enkephalin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1547-1563 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The average conformation of Met-enkephalin was determined by using an adaptive, importance-sampling Monte Carlo algorithm (SMAPPS - Statistical Mechanical Algorithm for Predicting Protein Structure). In the calculation, only the backbone dihedral angles (φ and ψ) were allowed to vary; i.e., all side-chain (χ) and peptide-bond (ω) dihedral angles were kept fixed at the values corresponding to a low-energy structure of the pentapeptide. The total conformational energy for each randomly generated structure of the polypeptide was obtained by summing over the interaction energies of all pairs of nonbonded atoms of the whole molecule. The interaction energies were computed by the program ECEPP/2 (Empirical Conformational Energy Program for Peptides). Solvent effects were not included in the computation. The calculation was repeated until a total of 10 independent average conformations were established. The regions of conformational space occupied by the average structures were compared with the regions of low conditional free energy obtained by SMAPPS in the first paper of this series. Such a comparison provides an analysis of the capacity of SMAPPS to adjust the Monte Carlo search to regions of highest probability. The results demonstrate that the ability of SMAPPS to focus the Monte Carlo search is excellent. Finally, the 10 independent average conformations and the mean of the 10 average structures were utilized as the initial conformations for a direct energy minimization of the pentapeptide. Of the 11 final energy-minimized structures, three of the conformations were found to be equivalent to the conformation of lowest energy determined previously. In addition, all but two of the remaining energy-minimized structures were found to correspond to one of the two other conformations of high probability obtained in the first paper of this series. These results indicate that a set of independent average conformations can provide a rational, unbiased choice for the initial conformation, to be used in a direct energy minimization of a polypeptide. The final energy-minimized structures consequently constitute a set of low-energy conformations, which include the global energy minimum.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250812
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  • 190
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    Estimation of the stability of globular proteins (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1623-1633 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interpretation of ΔGDH2O (the free energy change for the reaction, globular conformation ⇋ randomly coiled conformation, in the absence of denaturant), in terms of the free energies of transfer of various parts of the protein molecule from water to denaturant solution, is unsatisfactory because the latter are assumed to be identical to the transfer-free energies of similar groups attached to smaller model compounds. We have made empirical adjustments to transfer-free energy theory that make possible linear extrapolation of the free energy of denaturation of a protein from transition region to zero denaturant concentration. The modified theory, used to analyze the denaturation of proteins by guanidine hydrochloride and urea, allowed us to calculate reasonable values for Δα, the average change in accessibility to solvent of the component groups of protein.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250906
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  • 191
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    Prediction of protein structural class from the amino acid sequenceNRCC No. 25459. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1659-1672 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The multidimensional statistical technique of discriminant analysis is used to allocate amino acid sequences to one of four secondary structural classes: high α content, high β content, mixed α and β, low content of ordered structure. Discrimination is based on four attributes: estimates of percentages of α and β structures, and regular variations in the hydrophobic values of residues along the sequence, occurring with periods of 2 and 3.6 residues. The reliability of the method, estimated by classifying 138 sequences from the Brookhaven Protein Data Bank, is 80%, with no misallocations between α-rich and β-rich classes. The reliability can be increased to 84% by making no allocation for proteins classified with odds close to 1. Classification using previously developed secondary structural prediction methods is considerably less reliable, the best result being 64% obtained using predictions based on the Delphi method.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/bip.360250909
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  • 192
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    The distribution of charged groups in proteins (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1717-1733 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distributions of charged groups in 32 proteins of known three-dimensional structure have been analyzed to determine how regularly the groups are spread over the molecule's surfaces, and to identify and to study those proteins where charge asymmetry would seem important for their function. The distributions have been analyzed in terms of charge “polarity,” surface “charge density,” and electric dipole moments. More detailed studies of the distributions for individual proteins are made using map projections specifically developed for this purpose. In the light of the results obtained we discuss the role of charged groups in relation to protein function.
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    URL: http://dx.doi.org/10.1002/bip.360250913
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  • 193
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251001
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  • 194
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    Phosphorus nmr spectra of natural DNA fragments in the course of the B-to-A conformational transition (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1803-1812 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in the 31P-nmr spectra of sonicated natural DNA fragments were investigated in ethanol solutions where the fragments underwent, as checked by CD, the B-to-A conformational transition. The study produced the following conclusions: (1) The high DNA concentrations used for the 31P-nmr measurements promote the transition compared to dilute solutions that are commonly used for CD measurements. (2) The B-to-A transition was reflected in a cooperative downfield shift of the DNA 31P-nmr resonance, consistent with unwinding of the double helix. (3) Prior to the transition, the changes in chemical shift of double-and single-stranded DNAs were almost identical. It thus appears that the effect of ethanol on the geometry and hydration of phosphodiester linkages does not depend heavily on DNA base-base interactions. (4) The A-form resonances were 30-40% narrower than the B-form resonances, which is attributed to marked sequence-dependent variations in the latter conformation and to their reduction in the former. (5) The B-form DNA aggregated in the concentrated 31P-nmr samples in the presence of ethanol, judged from a milky opalescence of the solution and a substantial broadening of its 31P-nmr resonance. The broadening abruptly disappeared as soon as DNA adopted the A-form so that DNA, in dependence on the secondary structure, showed different tendencies to condense in the presence of ethanol. The condensation increased cooperativity of the B-to-A interconversion.
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    URL: http://dx.doi.org/10.1002/bip.360250917
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  • 195
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    Computer simulation of the folding-unfolding transition of island-model proteins - folding pathway, transition process, and fluctuations (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1815-1835 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo computer simulations were performed to elucidate the dynamic aspects of the folding and unfolding transitions of island-model protein. Five different types of model proteins were designed, according to characteristics of backbone structure. The computer simulations clearly show that the unfolding and folding transitions are all-or-none processes between the N-and U-states. They are typical Poisson processes. From the Arrhenius plots of rate constants, the activation enthalpies of folding and unfolding were determined. In addition, the folding pathways were determined along the reaction coordinate. Formations of several local structures along a polypeptide chain are almost simultaneous, but the most probable time sequence of events exists at the moment of transition. That is the most probable folding pathway. The unfolding pathway was found to be just the reverse process of the most probable folding pathway. The relationship between the fluctuations in each equilibrium state and the transition process was considered. In contrast to the theory of absolute reaction rate, the transient states are widely distributed along the reaction coordinate. From analysis of the “transient process,” we tried to determine the critical states from which the transient process starts. As a result, we found that the unfolding transition occurs at the stage near the N-state. During the U-state, large joined blocks rarely appear, but they appear in the transient process towards the N-state. However, the “branch point” between the N- and U-states lies near the N-state, and joined blocks tend to unfold prior to passing over the branch point. We concluded that the stability of later folding intermediates is important for selection of the folding pathway, while preferential selection of an early folding intermediate is important in acceleration of the folding rate. The effects of intrachain cross-linking and peptide fragment binding on the rate constants were examined by using computer simulations of model proteins. In general, a small-sized loop formed by cross-linking accelerates the folding rate and a large-sized loop contributes much to the stabilization of the native conformation. We also found that peptide fragment binding contributes little to the acceleration of the folding rate of the residual protein.
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    URL: http://dx.doi.org/10.1002/bip.360251002
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  • 196
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    Multiple denaturational transitions in fibrillar collagen (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1875-1893 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heat denaturation of pepsinized bovine nonfibrillar and fibrillar collagen was studied by differential scanning calorimetry. For fibrillar preparations that had been rapidly precipitated with stirring at low ionic strength, then resuspended at physiological ionic strength, multiple denaturational transitions were observed. At heating rates of 10°C/min, melting endotherms occurred at about 44, 50, 53, and 57°C. Fibrillar collagen that was slowly gelled without stirring at physiological ionic strength exhibited a similar series of endotherms, but the lower melting transitions were less conspicuous. In contrast, nonfibrillar bovine collagen in acidic solution showed only a single denaturational transition at 40°C. Nonfibrillar solutions at pH 7, to which inhibitors of fibrillogenesis were added, showed a major endotherm as high as 46°C. These results suggest that reconstituted fibrillar collagen contains a heterogeneous fibril population, possibly including molecules in a nonfibrillar state. It was proposed that the multiple melting endotherms of such preparations were due to sequential melting of molecular and fibril classes, each with a distinct melting temperature. The fibrillar classes may represent three or more types of banded and nonbanded species that differ from each other in packing order, collagen concentration, and possibly also in fibril width and level of cross-linking.
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    URL: http://dx.doi.org/10.1002/bip.360251006
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  • 197
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    Gramicidin S analogs with a D-Ala, Gly, or L-Ala residue in place of the D-Phe residue: Molecular conformations and interactions with phospholipid membrane (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2295-2307 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton nmr and CD spectra of gramicidin S (GS) cyclic-(Val1,1′-Orn2,2′-Leu3,3′-D-Phe4,4′-Pro5,5′)2 and of GS analogs - namely, [D-Ala4,4′]-GS, [Gly4,4′]-GS, and [L-Ala4,4′]-GS - were analyzed. The molecular conformation of [D-Ala4,4′]-GS is similar to that of GS, with the trans form about the D-Ala-Pro peptide bond. The molecular conformation of [Gly4,4′]-GS depends on the solvent composition of dimethylsulfoxide-d6/trifluoroethanol (DMSO)-d6/TFE and DMSO-d6/H2O as well as the solute concentration. In DMSO-d6 solution, [Gly4,4′]-GS forms the GS-type conformation of the monomer at lower concentration. At higher concentration, the GS-type conformer is converted to the other one that forms molecular aggregates. The cis form about the X-Pro peptide bonds is found for [Gly4,4′]-GS and [L-Ala4,4′]-GS in DMSO-d6 and for [L-Ala4,4′]-GS in TFE solution. The large temperature dependences of α-proton chemical shifts of [L-Ala4,4′]-GS in DMSO-d6 solution indicate that the conformer equilibrium changes with temperature. The GS-type conformation is not formed in [L-Ala4,4′]-GS. The two active peptide analogs, [D-Ala4,4′]-GS and [Gly4,4′]-GS, interact with the phospholipid membrane, taking the GS-type conformation. By contrast, an inactive analog, [L-Ala4,4′]-GS, does not interact with phospholipid membrane. The activities of GS analogs are found to correlate to the formation of the GS-type conformation upon binding with phospholipid membrane.
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    URL: http://dx.doi.org/10.1002/bip.360251207
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  • 198
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    Lateral packing of protofibrils in fibrin fibers and fibrinogen polymers (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2359-2373 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distinctive transverse banding pattern of fibrin fibers clearly indicates ordering of molecules in the longitudinal direction. In this study we examined the fibers of fibrin clots, as well as two types of fibrinogen polymers, by thin-section electron microscopy. The fibrinogen polymers have a transverse banding pattern identical to that of fibrin fibers - clearly indicating a regular longitudinal repeat - but they are larger in diameter, and show little or no branching. We therefore expected their overall ordering to be better than that of fibrin fibers. Several different fixation protocols were used. We readily observed the typical transverse banding seen previously by negative stain and metal replication techniques. However, only very rarely was any regular lateral lattice seen in any of the samples. X-ray diffraction was used to examine unfixed specimens of the two fibrinogen polymers and, once again, although a longitudinal repeat was evident, only rarely was evidence for lateral crystallinity seen. The electron-microscope and x-ray results showed that the needles and pellet fibers of fibrinogen have essentially the same internal architecture as thick fibrin fibers, and that all three types of polymer, although clearly transversely banded, have almost no crystallinity in their lateral protofibril packing.
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    URL: http://dx.doi.org/10.1002/bip.360251213
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  • 199
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    Electronic Resource
    Binding of porcine pancreatic secretory trypsin inhibitor to bovine β-trypsin: A kinetic study (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2325-2333 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the formation of the complex between bovine β-trypsin and the porcine pancreatic secretory trypsin inhibitor (PSTI; Kazal-type inhibitor) was investigated following the spectral changes associated with the displacement of proflavine from the enzyme, upon inhibitor binding, between pH 3.5 and 8.0 (I = 0.1M) at 21 ± 0.5°C. With inhibitor in excess over the enzyme ([PSTI] ≥ 5 × [bovine β-trypsin]), the time course of the reaction corresponds to a pseudo-first-order process. Over the whole pH range explored, the concentration dependence of the rate is second order at low PSTI concentrations but tends to first order at high inhibitor concentrations. This behavior may be explained by a relatively fast pre-equilibrium followed by a limiting first-order process. Values of kinetic parameters for PSTI binding to bovine β-trypsin depend, between pH 3.5 and 8.0, on the acid-base equilibrium of a single ionizing group (probably His-57 of bovine β-trypsin) that undergoes an acidic pKa shift from 7.0 in the free bovine β-trypsin to 5.5 in the enzyme:PSTI complex. Kinetics of the bovine β-trypsin:PSTI adduct formation has been analyzed and compared with that of other (pro)enzyme:inhibitor reactions. Considering the known molecular structures of free serine (pro)enzymes, of Kazal- and Kunitz-type inhibitors, as well as of their complexes, the binding behavior of PSTI to bovine β-trypsin has been related to the inferred stereochemistry of the proteinase:inhibitor contact region.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251210
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    Electronic Resource
    Electronic Resource
    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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