A Simple Method for Isolating DNA of High Yield and Quality from Cotton (shape Gossypium hirsutum L.) Leaves

An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase.     

Performing arts medicine.

Arts medicine has come of age, resulting from 3 important developments over the past decade: improved methods of diagnosis and treatment, an awareness that artists suffer from special problems related to their occupation and lifestyle, and the establishment of health programs emphasizing an interdisciplinary approach to these patients. We focus on the patterns of illness afflicting performing artists, specifically dancers, singers, actors, and instrumental musicians, and explain some of the things a health care team can do in treating these patients. The conditions governing these patients'' lives--early exposure to high expectations of excellence, incessant demands for perfection, long periods of intense practicing, fierce competition, high levels of anxiety associated with performance, and uncertain careers--need to be understood. Levels of disease and disability are remarkably high, but artists often ignore symptoms. We discuss the musculoskeletal, neurologic, vocal, psychological, and other syndromes found among performers and some of the difficulties in treating them. The prevention of injury, conservative management, collaboration with teachers, and a psychotherapeutic approach are desirable. Arts medicine programs for professional consultation exist in several major cities of the United States and abroad. Although research is needed regarding the effectiveness of health care services for performing artists, the scientific literature devoted to this field is growing.     

Methylated poly(L-lysine): conformational effects and interactions with polynucleotides

Methylated lysine, arginine and histidine residues are found in a number of proteins (for example, histones, non-histone chromosomal proteins, ribosomal proteins, calmodulin, cytochrome C, etc.). We are studying the effects of methylation on the conformations of poly(lysine) and of the effects of methylation of poly(lysine) and poly(arginine) on interactions with polynucleotides. The conformational properties of epsilon-amino-methylated poly(lysine) differ from those of unmodified poly(lysine). Methylation increases resistance to thermally-induced and NaCl-induced changes in the CD spectrum. Guanidinium chloride increases (proportional to the degree of methylation) the extent of approach to the conformation in dispute as to its being a random coil or an extended helix. Methylation enhances aggregation in the helix-inducing solvent 0.5 M Ca(ClO4)2. With increasing methylation of poly(lysine), the conformation in dodecyl sulfate changes from beta, to 50% alpha, to random coil at the maximum methylation. Increasing methylation of poly(lysine) weakens the interaction with polynucleotides in respect to dissociation by salt, linearly with methyl content. Complexes of (dAdT)n.(dAdT)n with the polypeptides are increasingly stabilized to heat denaturation by progressive methylation. However, with a series of synthetic double-stranded RNA's and DNA's a more complex situation exists, Tm increasing or decreasing, depending on the base composition, sequence and type of sugar. Methylation of poly(lysine) and poly(arginine) can have opposite effects on Tm based on results with complexes with (dI)n.(dC)n. Methylated poly(lysine) affects the CD spectrum of polynucleotides, in a manner dependent on base composition and sequence. In some cases large positive or negative psi-spectra are induced, which, in the case of (dGdC)n.(dGdC)n, can be positive or negative depending on the degree of methylation of the polypeptide and the salt concentration. It is suggested that the biological effects of methylation proteins may be evoke by salt changes in the cell cycle, and that methylation can affect local interactions with nucleic acids and larger scale structure, and interactions with lipids.     

Structure-function analysis of epidermal growth factor: site directed mutagenesis and nuclear magnetic resonance

The role of leucine-47 in determining the structure and activity of human epidermal growth factor was examined using site-directed mutagenesis. Wild type protein and four variants in which Leu47 was replaced by valine, glutamate, aspartate and alanine were produced from yeast. 1H NMR experiments demonstrated that substitution of Leu47 had little effect on the protein structure. The observed reduction in receptor binding affinity caused by the substitutions could thus be attributed to perturbation of a residue directly involved in receptor interactions.     

The length of the aminoacyl-acceptor stem of the selenocysteine-specific tRNA(Sec) of Escherichia coli is the determinant for binding to elongation factors SELB or Tu

Mutations in selC, which reduce the 8-base pair aminoacyl-acceptor helix to the canonical 7-base pair length (tRNA(Sec)(delAc] or which replace the extra arm of tRNA(Sec) by that of a serine acceptor tRNA species (tRNA(Sec)(ExS), block the function in selenoprotein synthesis in vivo (Baron, C., Heider, J., and B?ck, A. (1990) Nucleic Acids Res. 18, 6761-6766). tRNA(Sec), tRNA(Sec)(delAc), and tRNA(Sec)(ExS) were purified and analyzed for their interaction with purified seryl-tRNA synthetase, selenocysteine synthase and translation factors SELB and EF-Tu. It was found that seryl-tRNA synthetase displays 10-fold impaired Km and Kcat values for tRNA(Sec) in comparison to tRNA(Ser), decreasing the overall charging efficiency (Kcat/Km) of tRNA(Sec) to 1% of that characteristic for tRNA(Ser). tRNA(Sec)(ExS) was a less efficient substrate for the enzyme (Kcat/Km 0.2% of the tRNA(Ser) value) whereas the tRNA(Ser)(delAc) variant was charged with an approximately 2-3-fold improved rate compared to wild-type tRNA(Sec). Both mutant tRNA variants, when charged with L-serine, were able to interact with selenocysteine synthase to give rise to selenocysteyl-tRNA with tRNA(Sec)(ExS) being as efficient as wild-type tRNA(Sec). Seryl-tRNA(Sec)(delAc), on the other hand, was selenylated very slowly. Reduction of the length of the aminoacyl-acceptor stem to 7 base pairs prevented the interaction with translation factor SELB but allowed binding to EF-Tu, irrespective of whether tRNA(Sec)(delAc) was charged with serine or selenocysteine. The aminoacyl-acceptor helix of tRNA(Sec), therefore, is a major determinant directing binding to SELB and precluding interaction with EF-Tu.