Demonstration of protein-protein interaction specificity by NMR chemical shift mapping

Chemical shift mapping is becoming a popular method for studying protein-protein interactions in solution. The technique is used to identify putative sites of interaction on a protein surface by detecting chemical shift perturbations in simple (1H, 15N)-HSQC NMR spectra of a uniformly labeled protein as a function of added (unlabeled) target protein. The high concentrations required for these experiments raise questions concerning the possibility for non-specific interactions being detected, thereby compromising the information obtained. We demonstrate here that the simple chemical shift mapping approach faithfully reproduces the known functional specificities among pairs of closely related proteins from the phosphoenolpyruvate:sugar phosphotransferase systems of Escherichia coli and Bacillus subtilis.     

Surface Analytical Study of Synroc Subjected to Hydrothermal Attack

Specimens of the ceramic Synroc, both with (Synroc C) and without the addition of a simulated nuclear waste (Synroc B), were subjected to hydrothermal attack. The near-surface regions, both before and after attack, were characterized using X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. Ion-beam erosion was used in conjunction with these surface analysis techniques to obtain information from below the original surface. It was found that hydrothermal attack led to the formation of a modified layer extending to a maximum depth of ∼200 nm after 25 days at 350°C. Within this modified layer, the abundances and chemical states of the elements were different from those in the unattacked Synroc. The changes which were observed can be explained qualitatively by postulating that selective dissolution (e.g., for Ca and Ba), hydration (e.g., for Al and Fe), recrystallization (e.g., for Ti and Zr), and reaction with Co₂ dissolved in the liquid phase (e.g., to form CaCO₃) are all taking place.     

The association between fasting hyperbilirubinaemia and serum non-esterified fatty acids in man

1. The concentrations of plasma total and unconjugated bilirubin and of serum nonesterified fatty acids (NEFA) have been measured in two healthy subjects during fasts of up to 21 h. 2. Fasting was either continuous or interrupted by various procedures that altered the concentrations of NEFA and total bilirubin. 3. When NEFA concentrations were increased by the administration of noradrenaline, heparin or caffeine, bilirubin concentrations also rose. 4. When NEFA concentrations were lowered by insulin, bilirubin concentrations fell. 5. Meals of 3-138 kJ and more, taken during the fasting period, lowered total bilirubin and NEFA concentrations in both subjects, whereas the effects of smaller meals were less consistent. 6. These studies demonstrate a statistically significant correlation between total bilirubin and NEFA during uninterrupted fasting and an association between these variables under other experimental conditions. They suggest that the control of bilirubin concentrations in the blood is linked to lipid metabolism.     

Age-related variations in hepatic regeneration and erythropoietin production in the rat

Two hundred and thirty-five entrants into the MRC trial for mild to moderate hypertension were matched with control subjects in order to assess the psychological effects of a screening programme and recruitment into a clinical trial. The prevalence and incidence of psychiatric morbidity among the trial participants were compared with those of the controls by means of responses to a self-administered questionnaire and diagnostic psychiatric interviews. No differences among the groups were shown between screening and entry into the trial, but after entry the prevalence of psychiatric morbidity among the trial participants fell. This was due to a greater improvement of those with psychiatric symptoms at entry in this group, the incidence of new morbidity being similar among the groups.     

Antibody-induced antigen redistribution and shedding from human breast cancer cells

Cell surface antigens of human breast cancer cells undergo a rapid redistribution when bound by antibodies from cancer patients. The subsequent shedding of these antigen-antibody complexes and free antigen may be instrumental in tumor survival.     

On the mechanism underlying the action of D-600 on slow inward current and tension in mammalian myocardium

D-600 the methoxy derivative of verapamil, is said to affect the force of cardiac contraction and the slow inward current (LSi) specifically by reducing the membrane conductance for Ca2+ (gsi). However, it is apparent that many effects of D-600 cannot be adequately explained solely by an effect on gsi. We studied the effects of D-600 on membrane current and tension of cat papillary muscle, using a conventional single sucrose gap voltage clamp technique. The results indicate that D-600 not only reduces the maximal Ca conductance but also, depending on concentration and duration of exposure, alters both the kinetics of the Ca-carrying system and the amplitude of the steady state outward current. No changes in the steady state activation and inactivation variables or in the rate of Isi inactivation were found. However, a substantial increase in the time to peak Lsi, as much as 7 times normal, was observed after exposure to D-600 (0.5 X 10(-6) to 2.0 X 10(-6) M) for at least 20 minutes. Because approximately only 75% of the reduction in Lsi induced by D-600 could be attributed to change in the maximum value of gsi (gsi), we conclude that the change in time to peak and about 25% of the reduction in Isi must be due to a change in the activation kinetics of the Ca-carrying system, Calculations suggest that the time to 70% activation of gsi can be prolonged to as much as 10 times normal by prolonged exposure to negatively inotropic concentrations of D-600.