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21.
Further identification of the nature and linkage of the carbohydrate in hemoglobin A1c. 总被引:24,自引:0,他引:24
H F Bunn D N Haney K H Gabbay P M Gallop 《Biochemical and biophysical research communications》1975,67(1):103-109
We have found that Hb A1c contains neutral sugars which are only partially hydrolyzed from the N-termini of β chains. In both normal and diabetic Hb A1c, 0.2–0.3 equivalents of hexose were released, composed primarily of glucose and mannose in a 3:1 ratio. When Hb A1c was reduced with 3HNa BH4 and then treated with periodic acid, most of the radioactivity was recovered as 3H-formic acid with much lesser amounts of 3H-formaldehyde. From these results, we propose that in the red cell, glucose binds to the α-amino position of hemoglobin β-chains (valine) in an aldimine (Schiff base) linkage. This aldimine can then partially rearrange in a reversible manner to form a ketoamine linkage which is stable to acid hydrolysis. This Amadori-type rearrangement accounts for the formation of mannose, the C-2 epimer of glucose, as well as the inability to demonstrate 3HNa BH4 reduction at the C-1 position. 相似文献
22.
Background
Protective respiratory face masks protect the nose and mouth of the wearer from vapor drops carrying viruses or other infectious pathogens. However, incorrect use and disposal may actually increase the risk of pathogen transmission, rather than reduce it, especially when masks are used by non-professionals such as the lay public. Copper oxide displays potent antiviral properties. A platform technology has been developed that permanently introduces copper oxide into polymeric materials, conferring them with potent biocidal properties.Methodology/Principal Findings
We demonstrate that impregnation of copper oxide into respiratory protective face masks endows them with potent biocidal properties in addition to their inherent filtration properties. Both control and copper oxide impregnated masks filtered above 99.85% of aerosolized viruses when challenged with 5.66±0.51 and 6.17±0.37 log10TCID50 of human influenza A virus (H1N1) and avian influenza virus (H9N2), respectively, under simulated breathing conditions (28.3 L/min). Importantly, no infectious human influenza A viral titers were recovered from the copper oxide containing masks within 30 minutes (≤0.88 log10TCID50), while 4.67±1.35 log10TCID50 were recovered from the control masks. Similarly, the infectious avian influenza titers recovered from the copper oxide containing masks were ≤0.97±0.01 log10TCID50 and from the control masks 5.03±0.54 log10TCID50. The copper oxide containing masks successfully passed Bacterial Filtration Efficacy, Differential Pressure, Latex Particle Challenge, and Resistance to Penetration by Synthetic Blood tests designed to test the filtration properties of face masks in accordance with the European EN 14683:2005 and NIOSH N95 standards.Conclusions/Significance
Impregnation of copper oxide into respiratory protective face masks endows them with potent anti-influenza biocidal properties without altering their physical barrier properties. The use of biocidal masks may significantly reduce the risk of hand or environmental contamination, and thereby subsequent infection, due to improper handling and disposal of the masks. 相似文献23.
24.
Human aldose reductase and aldehyde reductase are members of the aldo-keto reductase superfamily that share three domains of homology and a nonhomologous COOH-terminal region. The two enzymes catalyze the NADPH-dependent reduction of a wide variety of carbonyl compounds. To probe the function of the domains and investigate the basis for substrate specificity, we interchanged cDNA fragments encoding the NH2-terminal domains of aldose and aldehyde reductase. A chimeric enzyme (CH1, 317 residues) was constructed in which the first 71 residues of aldose reductase were replaced with first 73 residues of aldehyde reductase. Catalytic effectiveness (kcat/Km) of CH1 for the reduction of various substrates remained virtually identical to wild-type aldose reductase, changing a maximal 4-fold. Deletion of the 13-residue COOH-terminal end of aldose reductase, yielded a mutant enzyme (AR delta 303-315) with markedly decreased catalytic effectiveness for uncharged substrates ranging from 80- to more than 600-fold (average 300-fold). The KmNADPH of CH1 and AR delta 303-315 were nearly identical to that of the wild-type enzyme indicating that cofactor binding is unaffected. The truncated AR delta 303-315 displayed a NADPH/D isotope effect in kcat and an increased D(kcat/Km) value for DL-glyceraldehyde, suggesting that hydride transfer has become partially rate-limiting for the overall reaction. We conclude that the COOH-terminal domain of aldose reductase is crucial to the proper orientation of substrates in the active site. 相似文献
25.
Ester S. Ramos Carlos A. Moreira-Filho Yvone A. M. V. A. Vicente Maria A. S. Llorach-Velludo Silvio Tucci Jr. Maria H. O. Duarte Amélia G. Araújo Lucia Martelli 《Human genetics》1996,97(5):596-598
Two 46,XX true hermaphrodites and one XX male without genital ambiguities are reported. They coexist in two generations of the same pedigree, with paternal transmission and in the absence of SRY (sex-determining region, Y chromosome). These familial cases provide evidence to support the hypothesis that these disorders are alternative manifestations of the same genetic defect, probably an autosomal dominant mutation (with incomplete penetrance) or an X-linked mutation (limited by the presence of the Y chromosome). 相似文献
26.
Formation of biologically active peptides 总被引:2,自引:0,他引:2
D F Steiner C Patzelt S J Chan P S Quinn H S Tager D Nielsen A Lernmark B E Noyes K L Agarwal K H Gabbay A H Rubenstein 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1980,210(1178):45-59
Many small biologicaly active peptides are derived from larger precursor forms which fulfil a variety of roles in the synthesis, segregation and intracellular migration of secretory products. Limited proteolysis may occur at several stages during this process, giving rise to products that are either degraded (e.g. the prepeptides) or discharged coordinately from their cells of origin during exocytosis (e.g. insulin and C-peptide). Molecular defects have recently been found to occur at cleavage sites in proinsulin as well as in other proproteins, and these point mutations may, in some instances, be responsible for familial metabolic disorders. The nature and cell specificity of the proteolytic enzymes involved in the conversion of the various precursor forms remains unresolved. Recent studies in our laboratory have led to the identification of precursors of glucagon and somatostatin in rat islets of Langerhans. Analysis of tryptic maps of these precursors has shown that a trypsin-like enzyme would be sufficient to cleave the C-terminally located somatostatin sequence from its precursor (relative molecular mass 12,500), but that both trypsin-like and carboxypeptidase B-like enzymes would be necessary to cleave the internal glucagon sequence from its prohormone (relative molecular mass 18,000). Molecular cloning techniques have provided valuable new approaches to analysing the structures of a variety of precursor forms, including those for insulin, gastrin, growth hormone, adrenocorticotropic hormone and the endorphins, and in the future will undoubtedly shed more light on the structures of their chromosomal genes, the mechanisms regulating their expression, and their evolutionary origins. 相似文献
27.
Specific interaction of peptides with nucleic acids 总被引:5,自引:0,他引:5
28.
In virgin females neurosecretory activity increased immediately after feeding. This is probably related to gut stretching. After one hour NSC numbers decreased until 48 hr after feeding. Thereafter NSC numbers showed oscillations until the 10th day. During this period rapid blood digestion takes place. The peak in NSC numbers found on the 10th day can be related to high O2 consumption and high protease activity. The peak in NSC number on the 14th day is possibly related to gut epithelial-cell proliferation. In mated and starved females no changes in NSC numbers could be found. Only when these females were fed, a marked increase in NSC was observed. A rise in NSC numbers observed during the period 5 to 15 days after mating could be related to oögenesis. Egg laying stimulated NS activity. It was found that certain types of NSC were connected with this phenomenon. A scheme is suggested to explain the interrelationship between the NSC in the CNS and physiological phenomena. 相似文献
29.
E J Gabbay R DeStefano C S Baxter 《Biochemical and biophysical research communications》1973,51(4):1083-1089
Proton magnetic resonance (pmr), ultraviolet absorption, induced circular dichroism (CD), and viscometric evidence is presented which show that reporter molecules and bind to DNA via an intercalation process. Preliminary kinetic studies show that the DNA· complex forms rapidly (i.e., <1 msec), whereas the DNA· complex forms at a considerably slower rate (). The kinetic results, and the steric requirements for intercalation of can be explained on the basis of a dynamic structure of DNA. 相似文献
30.