Interactions of the channel forming peptide alamethicin with artificial and natural membranes

Alamethicin and related α-aminoisobutyric acid peptides form transmembrane channels across lipid bilayers. This article briefly reviews studies on the effect of alamethicin on lipid phase transitions in lipid bilayers and on mitochondrial oxidative phosphorylation. Fluorescence polarization studies, employing 1,6-diphenyl-1,3,5-hexatriene as a probe, suggest that alamethicin fluidizes lipid bilayers below the phase transition t-emperature, but has little effect above the gel-liquid crystal transition point. Alamethicin is shown to function as an uncoupler of oxidative phosphorylation in rat liver mitochondria. The influence of alamethicin on mitochondrial respiration is modulated by the phosphate ion concentration in the medium. Classical uncoupling activity is evident at low phosphate levels while inhibitory effects set in at higher phosphate concentrations. Time-dependent changes in respiration rates following peptide addition are rationalized in terms of alamethicin interactions with mitochondrial membrane components

Molecular conformation of alamethicin in dimethylsulfoxide solution. A two-dimensional n.m.r. study

The solution conformation of alamethicin, a 20-residue antibiotic peptide, has been investigated using two-dimensional n.m.r. spectroscopy. Complete proton resonance assignments of this peptide have been carried out using COSY, SUPERCOSY, RELAY COSY and NOESY two-dimensional spectroscopies. Observation of a large number of nuclear Overhauser effects between sequential backbone amide protons, between backbone amide protons and CβH protons of preceding residues and extensive intramolecular hydrogen bonding patterns of NH protons has established that this polypeptide is in a largely helical conformation. This result is in conformity with earlier reported solid state X-ray results and a recent n.m.r. study in methanol solution (Esposito et al. (1987) Biochemistry26, 1043-1050) but is at variance with an earlier study which favored an extended conformation for the C-terminal half of alamethicin (Bannerjee et al. (1983) J. Mol. Biol.165, 757-775)

Cemented hemi-arthroplasty for unstable intertrochanteric fractures in the elderly: a retrospective study

Background: Unstable intertrochanteric fractures belonging to 31A2 and A3 varieties are difficult challenges for orthopaedic surgeons, particularly in the elderly patients. Osteosynthesis by dynamic hip screw or proximal femoral nail are often plagued by complications like screw cut-out, excessive collapse and fixation failures due to osteoporotic bones. Because of these complications, patients are often kept confined to the bed which may increase the risks of pressure sores, venous thrombosis and pulmonary infections. So, it is desirable to mobilize these elderly patients as quickly as possible following surgery. In recent decades, primary hemi-arthroplasty has emerged as a valuable treatment option for mobilizing these patients early.Methods: We present our retrospective study on 27 patients above 60 years of age, who were managed with cemented bipolar hemi-arthroplasty after sustaining unstable intertrochanteric fractures. All the patients were operated through modified Hardinge approach. The fractured fragments were secured by stainless steel wiring, particularly the greater trochanter, wherever necessary.Results: Twenty-three patients (85%) were able to stand up with walkers by third post-operative day and were able to walk by fifth post-operative day. There was one case of hip dislocation; it was reduced under anaesthesia. No other complications were encountered at an average follow-up of 3.1 years. The Harris hip score was ‘good’ or ‘excellent’ in more than 60% patients.Conclusions: Cemented hemi-arthroplasty appears to be a reliable treatment method for unstable intertrochanteric fractures in the elderly and it allows early weight-bearing and rehabilitation in most patients following surgery.

Sacrum metastasis in carcinoma gall bladder: an unusual presentation

Disseminated blood-borne metastases from carcinoma of the gall bladder are uncommon and usually occur late. The most common site of extra-abdominal metastasis is lung followed by brain. Skeletal metastases in carcinoma gall bladder are very rare. To date there have only been a few case reports of bone metastasis in carcinoma gall bladder at the time of presentation. Authors here present a rare case of carcinoma gall bladder that progressed to isolated sacrum metastasis.

A Thiazole Coumarin (TC) turn-on fluorescence probe for AT-base pair detection and multipurpose applications in different biological systems

Sequence-specific recognition of DNA by small turn-on fluorescence probes is a promising tool for bioimaging, bioanalytical and biomedical applications. Here, the authors report a novel cell-permeable and red fluorescent hemicyanine-based Thiazole Coumarin (TC) probe for DNA recognition, nuclear staining and cell cycle analysis. TC exhibited strong fluorescence enhancement in the presence of DNA containing AT-base pairs, but did not fluoresce with GC sequences, single-stranded DNA, RNA and proteins. The fluorescence staining of HeLa S3 and HEK 293 cells by TC followed by DNase and RNase digestion studies depicted the selective staining of DNA in the nucleus over the cytoplasmic region. Fluorescence-Activated Cell Sorting (FACS) analysis by flow cytometry demonstrated the potential application of TC in cell cycle analysis in HEK 293 cells. Metaphase chromosome and malaria parasite DNA imaging studies further confirmed the in vivo diagnostic and therapeutic applications of probe TC. Probe TC may find multiple applications in fluorescence spectroscopy, diagnostics, bioimaging and molecular and cell biology