The stability and unfolding of an IgG binding protein based upon the B domain of protein A from Staphylococcus aureus probed by tryptophan substitution and fluorescence spectroscopy

The stability and unfolding of an immunoglobulin (Ig) G bindingprotein based upon the B domain of protein A (SpAB) from Staphylococcusaureus were studied by substituting tryptophan residues at strategiclocations within each of the three a-helical regions (al-a3)of the domain. The role of the C-terminal helix, a3, was investigatedby generating two protein constructs, one corresponding to thecomplete SpAB, the other lacking a part of ct3; the Trp substitutionswere made in both one-and two-domain versions of each of theseconstructs. The fluorescence properties of each of the single-tryptophanmutants were studied in the native state and as a function ofguanidine-HCl-mediated unfolding, and their IgG binding activitieswere determined by a competitive enzyme-linked immunosorbentassay. The free energies of folding and of binding to IgG foreach mutant were compared with those for the native domains.The effect of each substitution upon the overall structure andupon the IgG binding interface was modelled by molecular graphicsand energy minimization. These studies indicate that (i) 3 contributesto the overall stability of the domain and to the formationof the IgG binding site in l and 2, and (ii) al unfolds first,followed by 2 and 3 together.     

Whither human cardiac spectroscopy?

Human cardiac magnetic resonance (MR) spectroscopy is presently comprised, almost exclusively, of phosphorus (³¹P) studies. These provide access to supply-side energy metabolism in the anterior myocardium of patients with hypertrophy, with cardiomyopathies including heart failure, with heart transplants, and with ischemic disease and myocardial infarction. A link between reduced phosphocreatine (PCr) to adenosine triphosphate (ATP) ratios and heart failure has been identified which might assist diagnosis in the presence of other confounding factors. PCr/ATP is often reduced in transplanted hearts for reasons not understood, but the ratio is presently an unreliable predictor of significant histological rejection for many patients. Myocardial infarction may reduce overall metabolite levels. In reversible myocardial ischemia,³¹P exercise stress-testing can produce reversible PCr/ATP reductions, at least in anterior disease: these seem to be specific for ischemic disease and may be helpful, especially if new technologies such as phased detector arrays and Overhauser enhancement can provide access to more of the heart. Human cardiac spectroscopy with nuclei other than³¹P may potentially access citric acid cycle metabolites, oxymyoglobin and deoxymyoglobin, and creatine levels, which may also be altered in heart failure.     

Impact of nano- and mesoscale particles on the performance of microcantilever-based sensors

Microcantilever-based sensors comprise an emerging class of chemomechanical sensors. The crucial challenge for every new and promising sensing platform lies in its performance in complex mixtures. Since most biofluids are rich in particulates, we assessed the impact of particles in the liquid stream on the performance of microcantilever sensors operated in both deflection and resonance modes. For both detection modes, sensor response depends on the particle diameter, concentration, and velocity as well as the composition of a thin-film coating. The presence of particles in the fluid stream produce substantial scattering of the laser beam used to measure cantilever deflection. Thus, prior removal of particulate matter from biofluids is required for optimal performance of microcantilever-based biosensors.     

Phase transformation in the binary section of the UO2-FeO-Fe system

Phase transformations in the oxide binary section of the UO₂-FeO-Fe ternary system were studied. The melting onset point of the UO₂-FeO heterogeneous system (1335±5°C) was determined and the fusion curve of this system was constructed. The limiting solubility of FeO in the UO₂ solid solution was measured. The changes in crystal parameters in formation of the solid solution were determined. Uranium dioxide was found to be insoluble in the wüstite phase (FeO).     

The effect of calcipotriol on lesional fibroblasts from patients with active morphoea

We examined the responsiveness of cultured dermal fibroblasts from biopsies of 6 patients with active morphoea and a similar number of matched controls to the cell proliferation inhibition activity of calcipotriol. Cultured fibroblasts from controls showed no significant response to calcipotriol (at concentrations of 1 x 10(-8) to 1 x 10(-4) M). However, calcipotriol did inhibit the proliferation response of morphoea fibroblasts at all concentrations when compared with controls. There was 4- to 20-fold inhibition in 2 of the morphoea patients when compared with control samples. Four other morphoea samples showed inhibition but to a lesser extent compared with controls.     

British Inflammation Research Association meeting: metalloproteinases and inflammatory diseases, the Fielder Centre, Hatfield, UK, 18 April 1997

Nitric oxide released by macrophages during inflammation reacts with active oxygen to form peroxynitrite. Peroxynitrite nitrates protein and peroxidizes lipids. gamma-Tocopherol traps peroxynitrite and is more effective than alpha-tocopherol in protecting lipids against such peroxidation.     

Digital calcification in systemic sclerosis: effective treatment with good tissue preservation using the carbon dioxide laser

Tissue calcification of the fingers associated with limited systemic sclerosis is a common problem and is the source of considerable morbidity as it may be extremely tender and cause considerable functional disability. The current treatment of digital calcification is unsatisfactory. We evaluated the use of the carbon dioxide (CO2) laser in the management of this condition in six patients with the limited form of systemic sclerosis. A total of 21 areas of symptomatic digital calcification of the fingers were treated. Complete resolution of symptoms occurred in 12, moderate response with partial improvement was seen in five, little improvement was observed in two, and recurrence of calcinosis was found in two. The patient's average healing time was 6 weeks (range 4-10). The median duration of follow-up was 20 months (range 12-40). Postoperative infection was seen in two patients, and resolved completely in both with the use of topical and oral antibiotics. We found the CO2 laser a simple and effective treatment for most of the symptomatic lesions of digital calcification, and it may obviate the need for deforming surgery in many cases.