类肌肽4(5)-丙氨酰胺-5(4)-羧酸咪唑的酶促合成及表征

肌肽(β-Ala-L-His)是一种高效抗氧化剂,广泛应用于生物、化工、医药等领域。应用微水相酶促合成类肌肽,效率高价格低,且具有相似性质,开发前景广阔。本研究以L-丙氨酸和4,5-二羧酸咪唑制备类肌肽4(5)-丙氨酰胺-5(4)-羧酸咪唑,正交实验下的最佳合成条件为:四氢呋喃:pH8磷酸缓冲溶液=10:1.6(V/V),L-丙氨酸:4,5-二羧酸咪唑=1:3(m/m),α-胰凝乳蛋白酶:底物=1:200(m/m),35oC下磁力搅拌1.5h。硅胶G60薄层色谱(TLC)分离反应产物,Rf=0.81处出现新斑点;刮下该点纯化后进行紫外扫描,高效液相色谱(HPLC)和核磁共振,紫外光谱253nm处吸收明显增强,310nm处出现新吸收峰;253nm、310nm、330nm高效液相色谱保留时间均为4.0min;13C核磁共振显示8组碳原子。结合胰凝乳蛋白酶的催化机理,得出产物结构为4(5)-丙氨酰胺-5(4)-羧酸咪唑。     

Synthesis and antioxidant properties of a new lipophilic ascorbic acid analogue

4-(4-Hydroxyphenyl)-5-(4-hydroxyphenylmethyl)-2-hydroxyfurane-2-one 1 was prepared by an acidic dimerisation of 4-hydroxyphenylpyruvic acid and some of its antioxidant and spectroscopic properties have been measured and compared to that of ascorbic acid. 1 is as good an antioxidant as ascorbic acid in the DPPH (2,2-diphenyl-1-picryl hydrazyl radical) test and the inhibition of hydroxyl radical and a powerful inhibitor of the Cu(2+) or AAPH (2,2'-azobis-(2-amidinopropane) dihydrochloride) induced oxidation of human LDL. 1 gives a stable radical characterised by its ESR spectrum similarly to ascorbic acid but in lower concentration and with a different reactivity towards nitroxides. Theoretical calculations allow us to propose the structure for the radical formed from 1, to explain its lower stability than ascorbyl radical and to evaluate the lipophilicity of 1.     

Synthesis of a cyclopentane amide DNA analogue and its base pairing properties

cpa-DNA monomers containing the bases adenine and thymine have been synthesized starting from the known compound 1 in 12 steps. Partially and fully modified cpa-thymidine and cpa-adenosine containing oligodeoxynucleotides were synthesized by standard oligonucleotide chemistry. Fully modified homo-cpa-A sequences lead to duplex destabilization by -1.4 degrees C/mod. relative to DNA. As its congener bca-DNA, cpa-DNA prefers left-handed duplex formation where possible.     

Synthesis and properties of the first all-aza analogue of a biologically active peptide

The synthesis of the first all-aza-amino acid analogue ( 2 ) of a peptidic renin inhibitor is described. The X-ray structural analysis and molecular modelling investigations of this novel compound reveal interesting conformational features which have a significant impact on its biological activity. In addition, insight into conformational features of azapeptides in general in comparison with the corresponding purely peptidic compounds is given.     

The radiation modifying properties of carnosine

The influence of carnosine (beta-alanyl-l-histidine) on the survival rate of albino mice subjected to whole-body X-irradiation has been investigated. Carnosine (50-200 mg/kg/day) administered per os during a period of 20 days before irradiation (5.0 Gy) increased the survival rate by 45-65%, whereas the administration of carnosine within 30 days after irradiation (5.5 Gy) produced an insignificant protective effect and caused inhibition of the postirradiation histamine accumulation in the spleen.     

Synthesis and its properties of oligonucleotide analogue containing thiocarbamate interlinkages.

Novel nucleotide analogues have been synthesized from morpholine subunits with thiocarbamate linkages. They indicated much stronger interaction with poly U or poly dT than the corresponding natural oligodeoxyribonucleotides. Solubility of the analogues in water was greatly enhanced by introducing sulfate groups at their both ends.     

The antioxidative properties of carnosine and other drugs

The antioxidative effect of various drugs on lipid peroxidation in rat serum in the presence of FeSO4 was studied. The concentration of TBA-active products decreased in the presence of carnosine and anticataract drugs (Japanese Catalin, Chinese Baineiting and Finnish Catachrom-OFTAN). Vita-iodurol (France) and Quinax (USA) were completely inert. One of feasible mechanisms underlying certain pathologies (cataract, rheumatism, etc.) is the damage of biomembranes by active oxygen species. The potent antioxidative activity of carnosine reflects the high therapeutic value of this compound.     

Ineupatoriol,a thiophene analogue of ichthyothereol,from Inula eupatorioides

Ineupatoriol, a thiophene analogue of ichthyothereol, was isolated from Inula eupatorioides. The absolute stereochemistry is that of ichthyothereol.     

Synthesis and opioid receptor binding properties of a highly potent 4-hydroxy analogue of naltrexone

Very high affinity for opioid receptors (e.g., K(i)=0.052nM for mu) has been observed in the rationally designed naltrexone analogue 5. SAR and physical data supports the hypothesis that the 4-OH group of 5 stabilizes the 3-carboxamido group in the putative bioactive conformation.     

Synthesis and antifungal activity of a ferrocene-fluconazole analogue

A novel ferrocene fluconazole analogue was synthesized and its antifungal properties investigated against yeast strains of medical importance, including those intrinsically resistant to fluconazole. In vitro tests revealed a slight increase in fungal growth and a reversal of the effect of fluconazole at minimal inhibitory concentrations.     

Synthesis of a fluorescent analogue of phosphatidylcholine

A fluorescent analogue of phosphatidylcholine was synthesized by acylation of 1-oleoyl-sn-glycero-3-phosphocholine with 6-N-(tert-butyloxycarbonyl)aminocaproic acid anhydride employing the catalyst 4-pyrrolidinopyridine. Removal of the protective group by treatment with HCl in chloroform was followed by subsequent reaction with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) to form the fluorescent analogue of phosphatidylcholine, 1-oleoyl-2-(NBD)aminocaproyl-sn-glycero-3-phosphocholine, in good yield and with high isomeric purity.     

Synthesis of a dihydroxythiophene analogue of catechosporines

A vinylogous cephalosporine bearing a dihydroxythiophene moiety as a potential catechol surrogate has been synthesised (I-e-beta). Even if the anti staphylococcus spectrum displayed by this compound is of interest, its activity against Pseudomonas species, expected for such a structure, remains disappointing.     

Anti-crosslinking properties of carnosine: significance of histidine

Carnosine, a histidine-containing dipeptide, is a potential treatment for Alzheimer's disease. There is evidence that carnosine prevents oxidation and glycation, both of which contribute to the crosslinking of proteins; and protein crosslinking promotes beta-amyloid plaque formation. It was previously shown that carnosine has anti-crosslinking activity, but it is not known which of the chemical constituents are responsible. We tested the individual amino acids in carnosine (beta-alanine, histidine) as well as modified forms of histidine (alpha-acetyl-histidine, 1-methyl-histidine) and methylated carnosine (anserine) using glycation-induced crosslinking of cytosolic aspartate aminotransferase as our model. beta-Alanine showed anti-crosslinking activity but less than that of carnosine, suggesting that the beta-amino group is required in preventing protein crosslinking. Interestingly, histidine, which has both alpha-amino and imidazolium groups, was more effective than carnosine. Acetylation of histidine's alpha-amino group or methylation of its imidazolium group abolished anti-crosslinking activity. Furthermore, methylation of carnosine's imidazolium group decreased its anti-crosslinking activity. The results suggest that histidine is the representative structure for an anti-crosslinking agent, containing the necessary functional groups for optimal protection against crosslinking agents. We propose that the imidazolium group of histidine or carnosine may stabilize adducts formed at the primary amino group.     

Synthesis and biological evaluation of a spongistatin AB-spiroketal analogue

The synthesis of a simplified analogue of the potent, cytotoxic tubulin-depolymerizing agent spongistatin 1, based on the AB spiroketal framework, is presented. The new structural analogue is an extension of a recently described spongistatin congener reported to disrupt microtubules in breast cancer cells in vitro and to alter the microtubule assembly reaction. Cytotoxicity data on the new structural analogue, as well as the parent congener, are reported. We found no significant cytotoxic or antitubulin activity with either compound.