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  • Analytical Chemistry and Spectroscopy  (37)
  • Cell & Developmental Biology  (3)
  • Photosynthetic acclimation  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Contrasting patterns of photosynthetic acclimation and photoinhibition in two evergreen herbs from a winter deciduous forest (1996)
    Springer
    Oecologia 107 (1996), S. 446-455 
    Details
    ISSN: 1432-1939
    Keywords: Forest understory ; Photosynthetic acclimation ; Photoinhibition ; Leaf longevity ; Nitrogen allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the microclimate within an Oak-Hickory forest and photosynthetic characters of two resident evergreen herbs with contrasting leaf phenologies was investigated on a monthly basis for 1 full year. Heuchera americana has leaf flushes in the spring and fall, with average leaf life spans of 6–7 months. Hexastylis arifolia produces a single cohort of leaves each spring with a leaf life span of 12–13 months. We predicted that among evergreen plants inhabiting a seasonal habitat, a species for which the frequency of leaf turnover is greater than the frequency of seasonal extremes would have a greater annual range in photosynthetic capacity than a species that only produced a single flush of leaves during the year. Photosynthetic parameters, including apparent quantum yield, maximum photosynthetic capacity (Pmax), temperature of maximum photosynthesis, photochemical efficiency of PSII and leaf nitrogen (N) and chlorophyll concentrations, were periodically measured under laboratory conditions in leaves sampled from natural populations of both species. Mature leaves of both species acclimated to changing understory conditions with the mean seasonal differences being significantly greater for Heuchera than for Hexastylis. Area based maximum photosynthetic rates at 25°C were approximately 250% and 100% greater in winter leaves than summer leaves for Heuchera and Hexastylis respectively. Nitrogen concentrations were highest in winter leaves. Chlorophyll concentrations were highest in summer leaves. Low Pmax/N values for these species suggest preferential allocation of leaf nitrogen into non-photosynthetic pools and/or light-harvesting function at the expense of photosynthetic enzymes and electron transport components. Despite the increase in photosynthetic capacity, there was evidence of chronic winter photoinhibition in Hexastylis, but not in Heuchera. Among these ecologically similar species, there appears to be a trade-off between the frequency of leaf production and the balance of photosynthetic acclimation and photoinhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333934
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthetic responses of Miconia species to canopy openings in a lowland tropical rainforest (1993)
    Springer
    Oecologia 94 (1993), S. 49-56 
    Details
    ISSN: 1432-1939
    Keywords: Miconia ; Tropics ; Rainforest ; Photosynthetic acclimation ; Canopy gaps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the photosynthetic acclimation of three tropical species of Miconia to canopy openings in a Costa Rican rainforest. The response of photosynthesis to canopy opening was very similar in Miconia affinis, M. gracilis, and M. nervosa, despite differences in growth form (trees and shrubs) and local distributions of plants (understory and gap). Four months after the canopy was opened by a treefall, photosynthetic capacity in all three species had approximately doubled from closed canopy levels. There were no obvious signs of high light damage after treefall but acclimation to the gap environment was not immediate. Two weeks after treefall, Amax, stomatal conductance, apprarent quantum efficiency, and dark respiration rates had not changed significantly from understory values. The production of new leaves appears to be an important component of light acclimation in these species. The only variables to differ significantly among species were stomatal conductance at Amax and the light level at which assimilation was saturated. M. affinis had a higher stomatal conductance which may reduce its water use efficiency in gap environments. Photosynthesis in the more shade-tolerant M. gracilis saturated at lower light levels than in the other two species. Individual plant light environments were assessed after treefall with canopy photography but they explained only a small fraction of plant variation in most measures of photosynthesis and growth. In conclusion, we speculate that species differences in local distribution and in light requirements for reproduction may be more strongly related to species differences in carbon allocation than in carbon assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317300
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  • 3
    Electronic Resource
    Electronic Resource
    Mass spectrometry of domoic acid, a marine neurotoxinNRCC No. 29369. (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 373-386 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Domoic acid is a naturally occurring amino acid, formerly available in limited amounts as a natural product of some algae of the family Rhodomelaceae. As the result of a recent incidence of toxicity in cultured blue mussels (Mytilus edulis) from a highly localized region of Atlantic Canada, useful amounts of this substance are likely to become available in the near future. Domoic acid is an important substance for fundamental studies in neurobiology as it possesses the highest affinity amongst known substances for the kainate receptors of the central nervous system. The present work describes fast atom bombardment (FAB) mass spectra of domoic acid, and of some of its isomers present in minor quantities in contaminated mussel extracts. These FAB spectra are subject to interferences from beam-inducced reduction reactions associated with matrices such as glycerol, but not with others such as 3-nitrobenzyl alcohol. Tandem mass spectrometry of the MH+ ions from these compounds is also reported. As a more feasible approach to quantitative analysis at trace levels, formation of the volatile tert-butyldimethylsilyl derivatives has been investigated and shown to be highly promising.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180604
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  • 4
    Electronic Resource
    Electronic Resource
    Fast atom bombardment/tandem mass spectrometry of physalaemin-like peptides (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 281-287 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fragment ion spectra obtained from collision-induced decomposition of protonated molecular ions have been used to determine amino acid sequences of several physalaemin-like peptides which were recently purified from rabbit stomach. This technique was chosen because the peptides were available in microgram quantities and were anticipated to contain pyroglutamate as the blocked N-terminal residue. Such spectra of several synthetic analogs of the naturally occurring peptides were obtained and analyzed to confirm the veracity of this peptide sequencing strategy. In addition, methyl ester derivatives of these synthetic peptides provided a crucial test for the spectral interpretation via the mass shifts thus induced.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140607
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of chromatographic and chromatographic/mass spectrometric techniques for the determination of polycyclic aromatic hydrocarbons in marine sedimentsNRCC No. 26728. (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 375-381 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The establishment of reliable values for concentrations of 16 priority pollutant polycyclic aromatic hydrocarbons (PAH) in a suite of marine sediment reference materials included an examination of the methods used to determine such compounds. Results from the five techniques used indicate large method biases. The biases arise from chemical interferences in methods which use non-selective measuring systems with separation techniques which do not first completely resolve the analytes; e.g., single-parameter optical detectors with high performance liquid chromatographic (HPLC) techniques or a flame ionisation detector (FID) with capillary column gas chromatographic (GC) methods. Measurement by a mass spectrometer with HPLC and GC removes much of the method bias. Results for a representative sediment are discussed to illustrate these conclusions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140805
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  • 6
    Electronic Resource
    Electronic Resource
    Fragmentation reactions of molecular dications of aromatic heterocyclic fused-ring compounds containing more than one nitrogen atomNRCC 33006. (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 89-96 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fragmentation reactions of both metastable and collisionally activated dications, formed by electron impact ionization of heterocyclic fused-ring aromatic compounds containing more than one nitrogen atom, were investigated. This work is an extension of similar work on analogous compounds containing just one nitrogen atom and on the related polycyclic aromatic hydrocarbons. The results obtained are interpreted in terms of mechanistic proposals concerning the competition between charge-separation and neutral-expulsion reactions, based on variations in diradical character with increasing molecular size and nitrogen content of these molecular dications.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270204
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  • 7
    Electronic Resource
    Electronic Resource
    Detection of fragment ions produced by collisional activation of multiply charged ions in a floated collision cell (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 151-155 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A scan law is derived for the detection of fragment ions formed by collisional activation (CA) of a multiply charged precursor in a floated collision cell of a tandem mass spectrometer. Comparisons of the CA spectra of multiply charged ions obtained in either a floated or a grounded collision cell demonstrate the benefits associated with raising the collision cell above ground potential. In addition to the advantages observed for singly charged ions, floating the collision cell increases the transmission of multiply charged ions through the first mass spectrometer by permitting higher source potentials to be used. This technique also increases the detection efficiency for products of charge separation reactions, which may prove useful in the charge state assignment of the fragment ions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270216
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  • 8
    Electronic Resource
    Electronic Resource
    Reaction-induced mass discrimination in XQQ instruments. Absolute cross-sections for N2+· + SF6 → N2 + SFx+ (x=1-5) (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 41-46 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Dynamically-correct branching ratios can be measured in a XQQ tandem mass spectrometer (MS/MS) under single-collision conditions when the key MS/MS parameters are properly selected to correct for reaction-induced mass discrimination within the RF-only quadrupole mass filter (Q2). The energy dependence of the cross-section, σ(E), for the reaction N2+· + SF6 → N2+SFx+ (x = 1-5) was measured in the NBS triple quadrupole (QQQ) tandem mass spectrometer. For P≃0.02-0.13 mTorr and E ≃ 5-60 eV (Lab) [the range of collision energies used for collisionally activated dissociation (CAD)], identical σ(E) were measured from both the rate of reactant ion decay and the rate of product ion formation. Therefore, these σ values are substantially free from kinetic interferences (i.e., no back reactions, no impurity reactions, no scattering losses, minimal fringing fields, no mass discrimination, well-defined gas target, etc.). Moreover, there is probably no significant systematic error in our measurements of the absolute σ values for N 2+· + SF6 → N2+SFx+ (x = 1-5) because the σ values we measured with this same technique for Ne +·+ Ne → Ne+Ne+·, Ar+· + Ar → Ar+Ar+·, and Ar+·+N2 → Ar+N2+· agreed well with literature values obtained with several well-established techniques.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020207
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  • 9
    Electronic Resource
    Electronic Resource
    An example of intense artifact peaks in mass analyzed ion kinetic energy spectra and their elucidation using an instrument of BEqQ configurationNRCC No. 28727. (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 79-83 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020502
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  • 10
    Electronic Resource
    Electronic Resource
    The determination of protein, oligonucleotide and peptide molecular weights by ion-spray mass spectrometry (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 249-256 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectra of several compounds with molecular weights in the 2500-20 000 Da range were obtained with a quadrupole mass spectrometer equipped with an atmospheric pressure ion source. Average molecular weight determinations of mellitin (2846.4 Da), a synthetic oligonucleotide (4262.8 Da), myoglobin (16 950.4 Da) and on the subunits of β-lactoglobulin (18 277.1 Da) requiring as little as 1 pmol of material were achieved with accuracies and precisions of ± 1 Da. An ion-spray interface was used to produce ions via the ion evaporation process, producing mass spectra containing a series of multiply-charged molecular species. A simple method for calculating the molecular weight of unknown compounds from the spectra containing multiply-charged ions is described.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290021111
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