One-flask synthesis of triacetalated aldohexoses with 2,2-dialkoxypropane and p-toluenesulfonic acid

2-Deoxy-d-arabino-hexose and some N-protected 2-amino-2-deoxy-d-glucose derivatives were each treated with 2,2-dimethoxy- or 2,2-dibenzyloxy-propane in 1,4-dioxane in the presence of p-toluenesulfonic acid at 60–70°. The major products were acyclic, dimethyl and dibenzyl acetals of 2-deoxy-3,4:5,6-di-O-isopropylidene-aldehydo-d-arabino-hexose or of N-protected 2-amino-2-deoxy-3,4:5,6-di-O-isopropylidene-aldehydo-d-glucose. Some of the dibenzyl acetals were converted into the corresponding 3,4:5,6-di-O-isopropylidene-aldehydo-d-hexoses in good yield.     

复合氨基酸注射液中L-色氨酸含量测定方法的研究

利用色氨酸结构中的吲哚基团在酸性条件下与对二甲氨基苯甲醛的特殊反应 ,在 6 10nm处测定复合氨基酸注射液中L 色氨酸的含量 ,获得满意的结果     

Modification of tryptophan and tryptophan residues in proteins by reactive nitrogen species.

Formation of 3-nitrotyrosine by the reaction between reactive nitrogen species (RNS) and tyrosine residues in proteins has been analyzed extensively and it is used widely as a biomarker of pathophysiological and physiological conditions mediated by RNS. In contrast, few studies on the nitration of tryptophan have been reported. This review provides an overview of the studies on tryptophan modifications by RNS and points out the possible importance of its modification in pathophysiological and physiological conditions. Free tryptophan can be modified to several nitrated products (1-, 4-, 5-, 6-, and 7-), 1-N-nitroso product, and several oxidized products by reaction with various RNS, depending on the conditions used. Among them, 1-N-nitrosotryptophan and 6-nitrotryptophan (6-NO(2)Trp) have been found as the abundant products in the reaction with peroxynitrite, and 6-NO(2)Trp has been the most abundant product in the reaction with the peroxidase/hydrogen peroxide/nitrite systems. 6-NO(2)Trp has also been observed as the most abundant nitrated product of the reactions between peroxynitrite or myeloperoxidase/hydrogen peroxide/nitrite and tryptophan residues both in human Cu,Zn-superoxide dismutase and in bovine serum albumin, as well as the reaction of peroxynitrite with myoglobin and hemoglobin. Several oxidized products have also been identified in the modified Cu,Zn-SOD. However, no 1-N-nitrosotryptophan and 1-N-nitrotryptophan has been observed in the proteins reacted with peroxynitrite or the myeloperoxidase/H(2)O(2)/nitrite system. The modification of tryptophan residues in proteins may occur at a more limited number of sites in vivo than that of tyrosine residues, since tryptophan residues are more buried inside proteins and exist less frequently in proteins, generally. However, surface-exposed tryptophan residues tend to participate in the interaction with the other molecules, therefore the modification of those tryptophans may result in modulation of the specific interaction of proteins and enzymes with other molecules.     

A spectroscopic probe of stacking interactions between nucleic acid bases and tryptophan residues of proteins.

The external heavy atom effect of mercury on the spectroscopic properties of the indole ring has been used to investigate stacking interactions of tryptophan with mercurinucleotides in mixed aggregates formed in frozen aqueous solutions as well as in oligopeptide-polynucleotide complexes. This effect is characterized at 77 K by a quenching of the tryptophan fluorescence, an enhancement of the phosphorescence emission and a drastic shortening of the phosphorescence lifetime. These phenomena result from an enhanced spin-orbit coupling due to a close contact between the mercury atom and the indole ring. Dissociation of the complexes leads to a recovery of the spectroscopic properties of the free tryptophan ring. The possible use of this spin-orbit probe to provide evidence for stacking interactions in protein-nucleic acid complexes is discussed.