Effect of chain length and concentration of anionic surfactants on the conformational transitions of poly(L-ornithine) and poly(L-lysine) in aqueous solution

The conformation of poly(L-ornithine) (PLO) and poly(L-lysine) (PLL) in solutions of sodium alkyl sulfates, CH₃(CH₂)_nSO₄Na with n = 7, 9, 11, 13 and 15 was studied by circular dichroism. PLO adopts a helical conformation in all 5 homologs and PLL a β-form in only 4 of the homologs. With octyl sulfate PLL has a helical conformation instead. These conformations were observed in solution of surfactants both below and above the critical micelle concentration.     

Gas-liquid chromatographic analysis of cyasin in cycad flour

A method for the quantitative determination of cycasin from cycad flour by gas-liquid chromatography is described. The flour is extracted with 70% ethanol and the residue from the dried extract is directly trimethylsilylated. Androsterone was found to be an excellent internal standard. The average content of cycasin from ten separate analyses of one lot of flour was $\text{0.429 gm}\text{100 gm}$. The method is rapid, sensitive, and not hindered by contaminating compounds.     

Characterization and Stability of Ribosomes from Mesophilic and Thermophilic Bacteria

Ribosomes were isolated from three mesophilic and three thermophilic strains of Bacillus. The ribosomes consisted of about 55% protein and 45% ribonucleic acid. Average ratios for the absorbance at 260/235 and 260/280 mmu were 1.77 and 1.92 for the mesophiles and 1.63 and 1.84 for the thermophiles. Ultracentrifugation revealed mainly components with sedimentation coefficients of about 30, 50, 70, 100, and 120S. All the preparations were shown to contain a ribonuclease which, in the presence of ethylenediaminetetraacetic acid, led to ribosome breakdown as measured by the increase in acid-soluble nucleotides. The stability of the ribosomes from the thermophiles was consistently greater than that of the ribosomes from the mesophiles. After 5 hr at 37 C, the breakdown was about 80% for the ribosomes from the mesophiles and 55 to 70% for those from the thermophiles. At 60 C, the ribosomes from the mesophiles were broken down slightly more and at a faster rate than those from the thermophiles. At temperatures above 60 C, the breakdown was again more pronounced for the ribosomes from the mesophiles.     

Role of the epithelium in airway smooth muscle responses to relaxant agonists.

We studied the role of the guinea pig tracheal epithelium in modulating tracheal smooth muscle responses to the relaxant agonists albuterol, sodium nitroprusside, and theophylline. We used an in vitro preparation that allowed separation of the fluids bathing the luminal (internal) and serosal (external) surfaces of the trachea, and bronchodilators were administered to either surface of carbachol-contracted tracheae. All three drugs produced dose-dependent relaxation. However, albuterol and nitroprusside were less potent (concentration that produced half-maximal effect increased by 100- and 32-fold, respectively) when given to the epithelial side with the epithelium intact compared with the epithelium denuded or compared with serosal administration with the epithelium intact. These differences were not observed for theophylline, where smooth muscle responses were independent of either the side of stimulation or of the presence or absence of the epithelium. Direct measurements of the diffusion of theophylline across the tracheal wall in the presence or absence of epithelium showed that after 5 h of incubation with a fixed luminal concentration of theophylline, only 1.7% had diffused across the tracheal wall with the epithelium intact. This increased to only approximately 3.3% when the epithelium was denuded. These results suggest that the epithelial is a relatively weak barrier for lipophilic agents but has a major role as a diffusion barrier to hydrophilic substances.