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481.
482.
An assay for the N-oxide metabolite of a benzazepine drug by fast atom bombardment ionization with tandem mass spectrometric analysis on a triple quadrupole mass spectrometer has been developed and validated for urine and plasma samples. This methodology allows analysis of this metabolite directly in crude sample extracts, without the need for extensive chromatography or sample derivatization. Quantification was accomplished with the use of a stable isotope analog of the analyte as an internal standard, using the selected reaction monitoring mode of operation. 相似文献
483.
The circular dichroic properties of H-Gly-Phe-(Gly)n-Trp-Gly-OH (II, n = 0,1,2) and of related simpler peptides, such as H-Phe-Gly-OH, H-Gly-Phe-OH, H-Gly-Phe-Gly-OH, H-Phe-Trp-OH, H-Phe-Trp-Gly-OH, and H-Gly-Phe-Trp-OH in water and trifluoroethanol solutions are investigated. Peptides containing only one phenylalanyl residue show markedly different near-uv dichroic signals depending on whether this residue is in the N-terminal position or not. The possible origin of this feature is discussed. The study of the oligopeptides II (n = 0,1,2) shows that no strong intramolecular interaction between the two aromatic rings is present. However, the dichroic properties of II (n = 0) are clearly anomalous, and the analysis of H-Gly-Phe-Trp-OH, H-Phe-Trp-Gly-OH, and of H-Phe-Trp-OH at different pH's, confirms that the presence of two adjacent aromatic residues may bring about chiroptical properties which indicate a restriction in the conformational equilibrium of the molecule. The limits, and the possible generalization of this finding, are discussed. 相似文献
484.
A solid state theory of oxidative phosphorylation 总被引:1,自引:0,他引:1
K D Straub 《Journal of theoretical biology》1974,44(2):191-206
A theory of oxidative phosphorylation utilizing phonons for energy transfer and chemical bond formation is presented. It is hypothesized that the phonons released during redox reactions of the electron transport chain can be propagated through the lattice structure of the proteins concerned with coupling. Energy loss of the phonons through rapid thermalization is prevented by hydrophobic bonding which serves as a thermal insulator of the lattice from the external environment. It is shown that respiratory control, reversed electron flow, uncoupling interchangability of energy among sites, utilization of two electron transfer to accomplish one bond formation are compatible with this theory. Experimental tests for the theory are proposed. 相似文献
485.
125I albumin was used to assess the amount of trapped fluid after microhematocrit centrifugation of erythrocytes suspended in buffers of different osmolality. Surprisingly the total amount of trapped fluid per volume unit of packed erythrocytes decreased with decreasing osmolality of the suspending buffer despite erythrocyte swelling. However, if the contribution of the individual erythrocyte to the trapped fluid was calculated, the trapped fluid per erythrocyte did not change between 311 mosm/kg and 256 mosm/kg. For osmolalities below 256 mosm/kg a significant increase of trapped fluid was obtained. It is concluded that the packing ability of erythrocytes is not impaired in suspending fluid of moderate to severe infraphysiological tonicity. The daily clinical experience that considerable degrees of plasma hypoosmolality are tolerated in vivo without hemolysis or impairment of oxygen transport by erythrocytes may be explained by the excellent ability of shape adaptation of erythrocytes to each other and to other surfaces such as vascular endothelia. The method of trapped fluid determination might be of potential value as a complementary method in the evaluation of erythrocyte rheology if the amount of trapped fluid is related to the individual erythrocyte. 相似文献