PubMed · 9246146
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D Emerton. 1997. Asthma guidelines.. https://pubmed.ncbi.nlm.nih.gov/9246146/
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The biochemical processes linked up to cyclic nucleotides related to the phenomenon of phagocytosis in Biomphalaria glabrata hemocytes were studied. In hemocytes the results suggest the presence of a phagocytic capacity similar to that observed in human cells related to regulation by cyclic adenylate monophosphate (cAMP), but not by cyclic guanylate monophosphate (cGMP). This similarity and differences in the metabolic process of phagocytary capacity between human phagocytary cells and hemocytes could represent an interesting model aimed at studying the phylogenetic evolution of enzymatic complexes.
Experimental thermodynamics studies and quantum chemical reaction path calculations on the hydrolytic degradation of Poly-vephyllinemalate microspheres in acidic and basic media were performed. It was possible to make a conclusion on the release mechanism of free Vephylline as follows: a hydrolytic cleavage of the ester bonds between molecular fragments of R,S-malic acid takes place and leads to a soluble oligoester fraction. Then, further hydrolysis of the ester bonds between the xanthine fragment and R, S-malic acid leads to the release of Vephylline as free base. The hydrolytic process takes place in acidic solution with rapid degradation of the ester bonds between the malic acid monomers and by far slower degradation of the ester bonds between the malic acid and Vephylline. In basic solution both steps of the hydrolysis are fast processes leading to a complete release of free Vephylline within 1 h. The process of Vephylline release is under entropic control. The experimental results are well correlated to the results obtained after kinetics investigation and after AM1 quantum chemically calculated energy barriers in the reaction path leading to the tetrahedral intermediates of the hydrolytic reactions. This conclusion is in good accordance with an indirect study on the release mechanism of Vephylline from its polymeric prodrug, paying attention to the biological response, reported previously.
Photocrosslinking allows first-order structural analysis with relatively small amounts of biological material and can be applied in complex in vitro systems. In this article we describe methods for positioning both arylazide and thionucleotide photoagents within an RNA of interest by end modification of circularly permuted RNAs. Application of this technique provided a library of constraints that, together with biochemical and phylogenetic comparative data, were used to develop a structure model of the bacterial ribonuclease P ribozyme-substrate complex. Circularly permuted genes for in vitro transcription are generated by PCR from tandem genes. Circularly permuted RNA transcripts can be modified with high efficiency at both the 5' and 3' termini with arylazide crosslinking reagents, or transcription can be primed with photoactive nucleotide analog monophosphates such as 6-thioguanosine. These crosslinking agents can be used over a wide range of experimental conditions but remain inert until they are activated by UV light. Crosslinked sites are subsequently mapped by reverse transcriptase primer extension of gel-purified crosslinked species. In addition to providing basic protocols for these methods, we discuss approaches for establishing the relevance of crosslinking data to native RNA structure.