High affinity binding of hydrophobic and autoantigenic regions of proinsulin to the 70 kDa chaperone DnaK

Background  

Chaperones facilitate proper folding of peptides and bind to misfolded proteins as occurring during periods of cell stress. Complexes of peptides with chaperones induce peptide-directed immunity. Here we analyzed the interaction of (pre)proinsulin with the best characterized chaperone of the hsp70 family, bacterial DnaK.     

The Neovessel Occlusion Efficacy of 151-Hydroxypurpurin-7-Lactone Dimethyl Ester Induced with Photodynamic Therapy

In this study, the photodynamic therapy (PDT) induced efficacy of a semi-synthesized analogue 15¹-hydroxypurpurin-7-lactone dimethyl ester or G2, in terms of chick chorioallantoic membrane blood vessel occlusion was evaluated in reference to verteporfin. Early formulation studies showed that G2 prepared in a system of cremophor EL 2.5% and ethanol 2.5% in saline was biocompatible up to 20 μL volume of injection. Following injection, G2 accumulation peaked within the first minute and its extravasation from intra- to extra-vascular occurred somewhat slower as compared with verteporfin. In the PDT study, closure of capillaries and small neovessels was observed with 4 μg per embryo of G2 and a light dose of 20 J cm⁻² at a fluence rate of 40 mW cm⁻² filtered at 400–440 nm—a result that may be considered optimum for the treatment of age-related macular degeneration (AMD). Also, partial occlusion of the large vessels was observed using the same dose of G2 and light—an effect which is desirable for cancer treatment. From this study, we conclude that G2 has the potential to be developed as a therapeutic agent for photodynamic treatment for AMD and cancer.     

Focused ion beam implantation of Ga in Si and Ge: fluence‐dependent retention and surface morphology

Focused ion beam implantation of 30‐keV Ga⁺ ions in single‐crystalline Si and Ge was investigated by SIMS, using Cs⁺ primary ions for sputtering. Nine different implantation fluences ranging from 1 × 10¹³ to 1 × 10¹⁷ Ga⁺‐ions/cm² were used, with implanted areas of 40 × 40 µm². The Ga concentration distributions of these implants were determined by SIMS depth profiling. Such 30‐keV Ga implantations were also simulated by a dynamic Monte‐Carlo code that takes into account the gradual change of the near‐surface composition due to the Ga incorporation. In both approaches, an essentially linear increase of the Ga peak concentrations with fluence is found up to ～1 × 10¹⁶cm^?2; for higher fluences, the Ga content approaches a saturation level which is reached at about (1–2) × 10¹⁷cm^?2. The measured and simulated peak concentrations of the Ga distributions are in good agreement. The most probable ranges obtained from the experiments correspond closely with the respective values from the simulations. The surface morphology caused by Ga⁺ implantation was investigated by atomic force microscopy (AFM). The AFM data indicate that for low fluences (<3 × 10¹⁵cm^?2) the surface within the implanted areas is growing outward (i.e. is swelling). For increasingly higher fluences, sputter‐induced erosion of the surface becomes dominant and distinct craters are formed for fluences above ～1 × 10¹⁶cm^?2. At the boundary of the implanted region a wall‐like structure is found to form upon Ga implantation; its height is growing with increasing fluence, reaching a value of ～15 nm at 1 × 10¹⁷ Ga⁺‐ions/cm². Copyright © 2008 John Wiley & Sons, Ltd.     

Diffusion Coefficients in Aqueous Solutions of Ammonium Monovanadate at 25°C

Differential diffusion coefficients of ammonium monovanadate in water at 25°C and at concentrations from 0.001 to 0.05 mol-dm^–3, have been measured using a conductimetric cell and an automatic apparatus to follow diffusion. The cell uses an open-ended capillary method and a conductimetric technique is used to follow the diffusion process by measuring the resistance of solutions inside the capillaries at recorded times.     

Electrochemical Oxidation of Guanosine and Xanthosine at Physiological pH: Further Evidences of a Convergent Mechanism for the Oxidation of Purine Nucleosides

The electrochemical oxidation of guanosine and xanthosine, which only differ in the presence of an oxygen atom at C2 position instead of an amine group, is studied on pyrolytic graphite electrodes at different electrolysis time scales in solutions of physiological pH. The oxidation products adsorbed on the electrode surface were electrochemical characterized in terms of variation of the formal potential with pH and catalytic activity towards the oxidation of NADH. The results were compared with those previously described for the oxidation of guanosine and adenosine in alkaline solutions. A common oxidation product is described, the oxidized form of 9‐β‐D ‐ribofuranosyluric acid, which is proposed as the point of convergence in the oxidation routes of all three purine nucleosides.     

The new high-pressure borate Co7B24O42(OH)2·2 H2O—Formation of edge-sharing BO4 tetrahedra in a hydrated borate

The new borate hydrate Co₇B₂₄O₄₂(OH)₂·2 H₂O was synthesized under high-pressure/high-temperature conditions of 6 GPa and 880 °C in a Walker-type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pbam (Z=2) with the lattice parameters a=819.0(2), b=2016.9(4), c=769.9(2) pm, V=1.2717(4) nm³, R₁=0.0758, wR₂=0.0836 (all data). The new structure type of Co₇B₂₄O₄₂(OH)₂·2 H₂O is built up from corner-sharing BO₄ tetrahedra forming corrugated layers, that are interconnected among each other by two edge-sharing BO₄ tetrahedra (B₂O₆ units) forming Z-shaped channels. Interestingly, the here presented structure of Co₇B₂₄O₄₂(OH)₂·2 H₂O is closely related to the structures of M₆B₂₂O₃₉·H₂O (M=Fe, Co), which exhibit BO₄ tetrahedra in an intermediate state on the way to edge-sharing BO₄ tetrahedra.     

An integrated workflow for extraction and solubilization of intermediate filaments from colorectal biopsies for proteomic analysis

We report a technique for isolation and solubilization of intermediate filament (IF) proteins from colonic biopsies compatible with both gel electrophoresis and liquid chromatography "shotgun" proteomics using mass spectrometry (MS). This is important because changes in the IF proteome, particularly in keratin expression and modification, are noted in colonic mucosa of patients with colorectal cancer. Though keratins have traditionally been dissolved in high concentration of urea, the latter solvent precludes efficient proteolytic digestion by trypsin prior to gel-free LC-MS/MS approaches. The extraction of cytoskeletal proteins was initially evaluated using MCF-7 cancer cell lines using a published, differential detergent solubilization protocol. IF proteins were extracted from colonic biopsies using a combination of homogenization and sonication. Since comparable efficiency of solubilization was noted on the extracted IF from cell lines between urea and guanidine hydrochloride (GuHCl) in triethylammonium bicarbonate buffer, isolated proteins from endoscopic biopsies were solubilized in GuHCl. Using immunoblotting techniques, we successfully demonstrated isolation of keratins and preservation of posttranslational modifications (phosphorylation, acetylation). Dissolved proteins were tryptically digested and peptides analyzed by MS, showing the functionality of the workflow in shotgun proteomic applications, specifically compatibility of the workflow for isobaric tagging relative and absolute quantification based quantitation approaches.