Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    International journal of food science & technology 34 (1999), S. 0 
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Profound differences in the rate of aggregation and denaturation among β-lactoglobulin samples from different sources can be reduced or even eliminated by dialysis of the samples first against a phosphate buffer. Visual evidence and thermograms indicated a reduced rate of aggregation in a phosphate buffered salt solution compared to the salt solution alone. The same effect was not achieved by another divalent tetrahedral ion, sulphate, nor by imidazole-buffered NaCl. Replacement of the background electrolyte by Na acetate had no discernible effect on the thermogram in the phosphate buffer. Phosphate is particularly good at buffering the protein solution at neutral pH at elevated temperature so the main effect is to maintain the net protein charge. In the imidazole and unbuffered media, the protein can move towards its isoelectric point and although the protein is more stable, aggregation is faster. It is speculated that there might also be a specific interaction of the phosphate anion with a cation-rich region of the β-lactoglobulin surface which could also inhibit aggregation at elevated temperatures.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Analytical results are given for whey powders prepared on a commercial or semi-commercial scale by three companies. Altogether, five preparations enriched in β-lactoglobulin, four whey protein isolates and a fraction enriched in α-lactalbumin were analyzed for protein composition, including %β-lactoglobulin, α-lactalbumin, bovine serum albumin, casein (glyco) macropeptide and the main triglycerides. Protein composition was determined by high pressure gel permeation and reversed phase liquid chromatography and by capillary zone electrophoresis. The extent of modification of the native β-lactoglobulin structure was also measured through the degree of lactosylation and the fraction of accessible free sulphydryl groups. One significant finding was that the calculated recovery of protein following quantitation of the chromatogram or electropherogram was seldom above 90% and occasionally below 60% of that loaded onto the column or capillary, raising doubts as to the reliability of the analytical results. Extrapolation by linear regression to 100% recovery allowed estimates to be made of the true β-lactoglobulin composition of the samples. The nine samples could be placed into three distinct groups with estimated true β-lactoglobulin weight % of 70.9 ± 1.1, 62.0 ± 3.4 and 39.5 ± 4.9. Physico-chemical properties of the group of samples are reported elsewhere (Holt et al., 1999).
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1365-2621
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The physico-chemical properties are reported for a group of whey protein powders prepared on a commercial or semi-commercial scale by three companies and chemically characterized as described elsewhere (Holt et al., 1999). The dependence of the apparent β-lactoglobulin % on the recovered % showed that the nine samples could be placed in three distinct groups with β-lactoglobulin weight % of 70.9 ± 1.1 (Group 1), 62.0 ± 3.4 (Group 2) and 39.5 ± 4.9 (Group 3). Measurements by 1H-NMR spectroscopy, on 3 of the samples confirmed that the native fold still predominated in the β-lactoglobulin. β-lactoglobulin could be crystallized from all the powders and the normal space group and cell dimensions were determined for the 8 samples that gave crystals of good enough quality for X-ray studies. Differential scanning microcalorimetry of samples dispersed in a phosphate buffer showed a clear difference between Goups 1 and 2 with a more prominent peak due to α-lactalbumin in the Group 2 samples. Light scattering and size exclusion chromatography showed that two types of aggregates were present to a variable extent in all the samples and after a heat treatment, the larger aggregates tended to predominate in Group 2. The rheology measurements, also made in the phosphate buffer, showed a difference of gel stiffness during heat treatment between the Group 1 and Group 2 samples with the exception of the BORCwpc+ sample. Within each group, gel stiffness increased with the degree of lactoslylation of the β-lactoglobulin. Interfacial measurements on samples dispersed in water presented a more complex pattern of behaviour although surface tension measurements at the air water interface of the Group 2 samples showed a two-step pattern of surface tension decrease with time, compared to a single step pattern in the Group 1 samples.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 534-535 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A vancomycin–N-acetyl-D-Ala-D-Ala complex has been crystallized by the sitting-drop vapour-diffusion method using imidazole maleic buffer at pH 7.6. The novel crystals obtained belong to the space group P6322 with unit-cell parameters a = b = 73.43 (1), c = 277.17 (4) Å, γ = 120°. The crystal density was determined as 1.106 g cm−3 which gives a supercell of 24 molecules (12 dimers) per asymmetric unit for an acceptable Matthews number and an estimated solvent content of 42%. Data were collected at room temperature to 2.8 Å.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...