Quadruplexes of human telomere DNA analogs designed to contain G:A:G:A,G:G:A:A,and A:A:A:A tetrads

Replacement of two to four guanines by adenines in the human telomere DNA repeat dG₃(TTAG₃)₃ did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three‐tetrad scaffold, as proved by CD and PAGE in both Na⁺ and K⁺ solutions. Thermodynamic data showed that, in Na⁺ solution, the dG₃(TTAG₃)₃ quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn‐guanosines. In physiological K⁺ solution, the highest destabilization was caused by the 4A tetrad. In K⁺, only the unmodified dG₃(TTAG₃)₃ quadruplex rearranged into a K⁺‐dependent quadruplex form, none of the multiple adenine‐modified structures did so. This may imply biological consequences for nonrepaired A‐for‐G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880–886, 2010.     

A History of Proteolipids: A Personal Memoir

This review is a personal memoir of the history of proteolipids and is limited to aspects of the field with which the author has been involved in one way or another. The discovery of proteolipids was a serendipitous observation made in the course of the study of sulfatides. Initial focus was on the chemical characterization of brain proteolipids, their behavior under different conditions and their identification as the major protein of CNS myelin. The sequence of PLP was obtained using solid phase protein sequencing techniques. This, in turn, made possible a new era in which biochemical, cellular and molecular approaches could be applied to address new questions about PLP. Identification of genetic defects in the PLP molecule and its regulation has contributed to understanding myelin biology. Studies of the encephalitogenic activity of PLP in animal models have influenced the views of inflammatory processes in multiple sclerosis. Despite remarkable progress, much remains to be learned about the structure and function of PLP.     

A rapid assay of acyl-coenzyme A:lysolecithin acyltransferase activity

A simple and rapid procedure for the assay of acyl-coenzyme A:1-acyl-sn-glycero-3-phosphocholine acyltransferase (lysolecithin acyltransferase, LLAT [EC 2.3.1.23]) activity in crude enzyme preparations is described. The incubation system utilizes lysolecithin and [1-14C]-oleoyl-coenzyme A as substrates. Labeled fatty acid released due to accompanying acyl-coenzyme A hydrolase [EC 3.1.2.2]activity is first removed by di-isopropyl ether extraction. The labeled lecithin produced due to LLAT action is then quantitatively recovered by partition of the incubation medium with di-isopropyl ether-n-butanol 60:40 (v/v). Selective extraction of the labeled lecithin formed and avoidance of customary thin-layer chromatographic isolation procedures permits assay of LLAT activity with excellent accuracy at a substantial saving of time. The entire assay can be completed in less than 30 min as compared to 2-3 hrs when following conventional procedures.     

S-trifluoroacetonyl-coenzyme A:a 19F analogue of acetyl-coenzyme A

S-Trifluoroacetonyl-coenzyme A has been synthesized in 87% yield by reaction of 1,1,1-trifluoro-3-bromopropanone with trilithium coenzyme A in presence of pyridine. The compound was characterized by its ultraviolet absorption spectrum and 1H and 19F nuclear magnetic resonance spectra. The alpha-methylene protons of the S-trifluoroacetonyl group exchanged with D2O and showed a pKa of 9.85 in S-trifluoroacetonylmercaptoethanol. S-Trifluoroacetonyl-coenzyme A is a competitive inhibitor of porcine heart citrate synthetase (Ki = 0.16 mM). It forms a binary complex with the enzyme and a ternary complex with enzyme/oxaloaetate binary complex, as evidenced ty the 19F shift. S-Trifluoracetonyl-coenzyme A and S-trifluoroacetonylmercaptoethanol form weak to moderately strong complexes with alpha-cyclodextrin and show little or no interaction with the methylglucose polysaccharide and lipopolysaccharides from Mycobacterium smegmatis [Smith, W. L., & Ballou, C. E. (1973) J. Biol. Chem. 248, 7118]. S-Trifluoroacetonylmercaptoethanol probably forms an inclusion complex with alpha-cyclodextrin because the interaction is reversed by compounds that do form inclusion complexes.