Hydrolytic microbial resolution of 1,2-O-isopropylidenglycerol: Improvements by using esters with homologous fatty acids

Summary The possibility of obtaining chiral 1,2-O isopropylidenglycerol by hydrolysis of its esters with homologous fatty acids from C₃ to C₇ was investigated withSarcina lutea, Pseudomonas putida, andBacillus subtilis var.niger. With the latter the degree of enantioselectivity increases with increasing chain length to a maximum of 82% e. e. of the S enantiomer in the hydrolysis of hexanoyl 1,2-0-isopropylidenglycerol.     

Stereoselective reduction of non-cyclic carbonyl compounds by some eumycetes

Summary Twelve strains of Eumycetes were able to perform the reduction of 2-pentanone, acetophenone and ethyl acetoacetate, sometimes in a yield suitable for preparative work. For each substrate, preferential reduction to the R-configurated alcohol was observed with one or more strains.     

Cooperative 3-epimerization of chenodeoxycholic acid byClostridium innocuum andEubacterium lentum

In the course of an in vitro screening of intestinal microorganisms from human feces to assess their ability to perform 3-hydroxy epimerization of chenodeoxycholic acid, we isolated aClostridium innocuum strain with 3-hydroxysteroid dehydrogenating activity; this, when cocultured with a strain ofEubacterium lentum able to produced small amounts of the 3-epimer from chenodeoxycholic acid, was able to markedly strengthen the transformation. The activity of both strains has been tested on 3-oxo-CDCA and on 3-hydroxy-CDCA in an effort to clarify the cooperative epimeric conversion.     

Human hnRNP protein A1: A model polypeptide for a structural and genetic investigation of a broad family of RNA binding proteins

The hnRNP fiber is the substrate on which pre-mRNA processing occurs. The protein moiety of the fiber (hnRNP proteins) constitutes a broad family of RNA binding proteins that revealed, upon molecular analysis, a number of interesting features.Heterogeneous nuclear ribonucleoprotein A1 is a major component of the human hnRNP complex. In recent years this protein has attracted great attention because of several emerging evidences of its direct involvement in pre-mRNA processing and it has become one of the best characterized RNA binding proteins. Detailed knowledge of the structure of protein A1 has laid the basis for the understanding of its function, and for this reason A1 can be considered as a model polypeptide for the investigation of a large number of RNA binding proteins.In this work we report recent findings regarding the binding properties of protein A1 as well as new data on the gene structure of A1 and of its closely related hnRNP protein A2. Our results show that a single A1 molecule contains the determinants for simultaneous binding of two single-stranded nucleic acid molecules and we demonstrate that the glycine-rich domain of A1, isolated from the rest of the molecule, is capable of sustaining protein-protein interactions. These features probably account for the reannealing activity of the protein and for its capacity to modulate the binding of snRNPs to intron sequencesin vitro. Comparison of A1 and A2 gene sequences revealed a remarkable conservation of the overall structural organization, suggesting important functions for the different structural elements.     

Relationship between cytotoxicity and induction of sister-chromatid exchanges in mouse foetal cells exposed to several doses of carcinogenic and non-carcinogenic chemicals.

The increase in sister-chromatid exchanges induced by 5 chemicals, with different DNA damaging and carcinogenic activities, was studied in short-term foetal-mouse cultures. A significant increase in SCE was induced by N-methyl-N'-nitro-N-nitrosoguanidine, N-diazoacetylglycine-amide, azaserine and methotrexate. k-Strophantin, on the contrary, was totally inactive. On a molar basis, MNNG was the most active chemical followed by MTX, AZS and DGA, in that order. At equitoxic concentrations (D37), the order of SCE-inducing abilities was MNNG, DGA, AZS and MTX. Compared with previous data, at equitoxic concentrations, the most DNA-damaging agents were also the most effective in inducing SCE. The SCE increase seems to correlate not with unspecific cytotoxicity but more with DNA damage or other damage at the genome level. MTX, a non-mutagen, which induced SCE only at toxic levels, could be considered a false positive because this positivity may reflect an enhancement of incorporation of 5-BrdUrd into DNA. The positive results obtained with AZS suggest a sufficient sensitivity of the method for detecting relatively weak carcinogens.     

Fluoride resistant alpha-naphthyl acetate esterase and combined enzyme histochemistry in the study of normal and pathologic lymphoid tissues

Alpha-Naphthyl acetate esterase (ANAE) and fluoride resistant alpha-naphthyl acetate esterase (FRANAE) have been compared as histochemical methods to identify T lymphocytes in sections of normal and pathological human lymphoid tissues. In addition, the FRANAE method was combined with alkaline phosphatase (ALP) in order to simultaneously evaluate the relationship between T lymphocytes and fibroblastic reticular cells (ALP) positive). The "dot like" esterase positivity of T lymphocyte was better evaluated by using FRANAE when compared to ANAE because of fluoride inhibitor of the strong esterase activity of dendritic cells and most macrophages. The combined ALP-FRANAE method clearly demonstrated a large number of fibroblastic reticular cells within the T-areas in various normal and pathological tissues such as hyperplastic lymph nodes and especially in the lymph nodes and spleens from patients with Hodgkin's disease.     

Stereoselective reduction of non-cyclic ketones with lactic acid bacteria

Summary The ability to reduce 2-pentanone, ethyl acetoacetate and acetophenone was investigated among lactic acid bacteria. Results show that this transformation is not performed by homofermenting lactic acid bacteria, while heterofermenting species can reduce the substrates to the corresponding S alcohol in satisfactory yields, often with 100% optical purity.     

Evidence for involvement of ketoglutarate in the biosynthesis of Canthin-6-one from cell cultures of Ailanthus altissima

¹³C enrichments at C-3, C-4, C-5 and C-6 of canthin-6-one from cell cultures of Ailanthus altissima supplemented with [1-¹³C], [2-¹³C] and [1,2-¹³C] acetate, give evidence of the involvement of ketoglutarate as an intact precursor in the biosynthetic pathway.     

A study on the mechanism of the epimerization at C-3 of chenodeoxycholic acid by Clostridium perfringens.

The mechanism of 3-hydroxy epimerization of chenodeoxycholic acid by Clostridium perfringens was investigated in 3 alpha, 7 alpha-dihydroxy-[2,2,4,4-2H4]-, 3 alpha, 7 alpha-dihydroxy-[3 beta-2H]- and 3 beta, 7 alpha-dihydroxy-[3 alpha-2H]-5 beta-cholanoic acid transformations. Our findings rule out a dehydration-rehydration pathway and agree with a redox mechanism involving 3-oxochenodeoxycholic acid as intermediate.