The presence of two modes of binding to calf thymus DNA by metal-free bleomycin: a low frequency Raman study

Double-stranded DNA is targeted by bleomycin in cancer cells and ambiguity exists as to its mode of DNA binding. A conventional Raman study was performed on drug/DNA complexes in which the low frequency spectral region (560-930 cm(-1)) was examined at two temperatures (19 and 30 degrees C). At 30 degrees C, a global Raman hypochromism was observed consistent with partial intercalation of the bithiazole moiety. At 19 degrees C, Raman hypochromism (increased base pair stacking) was detected for bands associated with GC base pairs while Raman hyperchromism (base pair destacking) was evident for bands associated with AT base pairs. These results suggest that intercalation of the bithiazole moiety occurs with greater disruption of the more efficiently stacked AT base pairs at the lower temperature. Evidence for minor groove binding was indicated by an increase in the population of bands corresponding to C3' endo sugar conformations resulting from drug induced local desolvation of the DNA polymer.     

Fluorescence X-ray absorption studies of rubredoxin and its model compounds

The X-ray absorption spectra of rubredoxin from Peptococcus aerogenes and of the model iron sulfur components prepared by Holm [Fe(S₂-O-xyl)₂] have been obtained in the oxidized and reduced forms using X-rays from synchrotron radiation at the Stanford Synchrotron Radiation Project. The spectra were measured both in transmission and by fluorescence, with the latter giving a several-fold higher signal-to-noise ratio for the protein. The edge spectra of the protein and the model compounds were extremely similar and both showed similar changes upon reduction. The best resolved change of the edge spectra upon reduction was a shift of the 1s-3d transition by ≈0.7 eV to lower energies. The EXAFS region of the spectra were converted to k-space and the data were fitted in order to determine first the average Fe-S distances, R_ave, and second their spread which, for rubredoxin, was described by a model wherein three Fe-S bonds had length R₃ and one R₁.Three different methods have been tried consisting essentially of fitting (1) both phase and amplitude simultaneously to the R₃, R₁ model, (2) phase alone to an R_ave model and using the phase to determine the spread of distance, and (3) using phase and amplitude to fit an R_ave model and then using the amplitudes alone to determine the spread of distances. The values of R_ave obtained for the oxidized state of rubredoxin were $\text{R}{}_{\mathrm{<mtext>ave</mtext>}}\text{= 2.265(13)}\text{A}\text{?}$ for the powder and 2.256(16) Å in solution. Upon reduction the value increased to 2.32(2) å. The spread of the distances was determined most accurately by the third method and was $\text{¦R}{}_3\text{— R}{}_1\text{¦= 0.04}{}^{\mathrm{+0.06}}{}_{\mathrm{?0.04}}\text{A}\text{?}$ for the oxidized powder and $\text{¦R}{}_3\text{— R}{}_1\text{¦= 0.08}$ for the reduced form. These values agree within combined experimental errors with the values found by extended X-ray absorption fine structure in the oxidized and reduced forms of Fe(S₂-O-xyl)₂, which also agreed with the previously published X-ray diffraction results.The agreement between the average distances in rubredoxin and the model compounds and the small spread allowable in the rubredoxin distances lead to the conclusion that any strain energy in the iron — sulfur bonds of Rub_ox is appreciably less than thermal energy. Hence the redox potential is not being regulated by strain in the iron — sulfur bond lengths.     

Prion infection of skeletal muscle cells and papillae in the tongue

The presence of the prion agent in skeletal muscle is thought to be due to the infection of nerve fibers located within the muscle. We report here that the pathological isoform of the prion protein, PrP(Sc), accumulates within skeletal muscle cells, in addition to axons, in the tongue of hamsters following intralingual and intracerebral inoculation of the HY strain of the transmissible mink encephalopathy agent. Localization of PrP(Sc) to the neuromuscular junction suggests that this synapse is a site for prion agent spread between motor axon terminals and muscle cells. Following intracerebral inoculation, the majority of PrP(Sc) in the tongue was found in the lamina propria, where it was associated with sensory nerve fibers in the core of the lingual papillae. PrP(Sc) staining was also identified in the stratified squamous epithelium of the lingual mucosa. These findings indicate that prion infection of skeletal muscle cells and the epithelial layer in the tongue can be established following the spread of the prion agent from nerve terminals and/or axons that innervate the tongue. Our data suggest that ingestion of meat products containing prion-infected tongue could result in human exposure to the prion agent, while sloughing of prion-infected epithelial cells at the mucosal surface of the tongue could be a mechanism for prion agent shedding and subsequent prion transmission in animals.     

Phosphorylation of Syk activation loop tyrosines is essential for Syk function. An in vivo study using a specific anti-Syk activation loop phosphotyrosine antibody

Syk is an important protein-tyrosine kinase in immunoreceptor signaling. FcepsilonRI aggregation in mast cells induces tyrosine phosphorylation and increased enzymatic activity of Syk. The two adjacent tyrosines in the Syk activation loop are thought to be important for the propagation of FcepsilonRI signaling. To evaluate the phosphorylation of these tyrosines in vivo and further understand the relationship of Syk tyrosine phosphorylation with its function, an antibody was developed specific for phosphorylated tyrosines in the activation loop of Syk. FcepsilonRI aggregation on mast cells induced the phosphorylation of both tyrosine residues of the activation loop. The kinase activity of Syk played the major role in phosphorylating its activation loop tyrosines both in vivo and in vitro. In FcepsilonRI-stimulated mast cells, the total Syk tyrosine phosphorylation paralleled the phosphorylation of its activation loop tyrosines and downstream propagation of signals for histamine release. In contrast, the cell surface binding of anti-ganglioside monoclonal antibody AA4 induced only strong general tyrosine phosphorylation of Syk and minimal histamine release and weak phosphorylation of activation loop tyrosines. These results demonstrate that phosphorylation of the activation loop tyrosines is important for mediating receptor signaling and is a better marker of Syk function than is total Syk tyrosine phosphorylation.     

Inverting character of alpha-glucuronidase A from Aspergillus tubingensis

Alpha-glucuronidase A from Aspergillus tubingensis was found to be capable of liberating 4-O-methyl-D-glucuronic acid (MeGlcA) only from those beechwood glucuronoxylan fragments in which the acid is attached to the non-reducing terminal xylopyranosyl residue. Reduced aldotetrauronic acid, 4-O-methyl-D-glucuronosyl-alpha-1,2-D-xylopyranosyl-beta-1,4-xylopyranosyl-beta-1,4-xylitol, was found to be a suitable substrate to follow the stereochemical course of the hydrolytic reaction catalyzed by the purified enzyme. The configuration of the liberated MeGlcA was followed in a D(2)O reaction mixture by (1)H-NMR spectroscopy. It was unambiguously established that MeGlcA was released from the substrate as its beta-anomer from which the alpha-anomer was formed on mutarotation. This result represents the first experimental evidence for the inverting character of a microbial alpha-glucuronidase, a member of glycosyl hydrolase family 67 (EC 3.1.1.139).     

Safety and toxicological evaluation of a novel niacin-bound chromium (III) complex

Chromium is an essential trace element required for normal protein, fat and carbohydrate metabolism. It also helps in energy production and increasing lean body mass. Niacin-bound chromium (NBC) is a unique form of bioavailable chromium that promotes healthy lipid profile. This study was focused on determining the broad spectrum safety of NBC. Acute oral, acute dermal, primary dermal irritation and primary eye irritation toxicities of NBC were evaluated. Ames bacterial reverse mutation assay, mouse lymphoma test and a dose-dependent 90-day subchronic toxicity were also conducted. In safety studies, the acute oral LD(50) of NBC was found to be greater then 5000 mg/kg in both male and female Sprague-Dawley rats. No changes in body weight or adverse effects were observed following necropsy. The acute dermal LD(50) of NBC was found to be >2000 mg/kg. The primary skin irritation test was conducted with NBC on New Zealand Albino rabbits. NBC was classified as slightly irritating. The primary eye irritation test was conducted with NBC on rabbits. NBC was classified as practically non-irritating to the eye. NBC did not induce mutagenic effects in the bacterial reverse mutation test in five Salmonella typhimurium strains (TA1535, TA98, TA100, TA97a and TA102), either with or without metabolic activation. Similarly, NBC did not induce mutagenic effects in the mammalian cell gene mutation test in L5178Y mouse lymphoma cells TK (+/-), either with or without metabolic activation. A dose-dependent 90-day subchronic toxicity study demonstrated no significant changes in selected organ weights individually and as percentages of body and brain weights. NBC supplementation did not cause changes in hepatic lipid peroxidation or DNA fragmentation after 30, 60 or 90 days of treatment. Hematology, clinical chemistry and histopathological evaluations did not show any adverse effects in all organs tested. Taken together, the above results indicate a broad spectrum of safety for NBC.     

An architecture for biological information extraction and representation

Motivations: Technological advances in biomedical research are generating a plethora of heterogeneous data at a high rate. There is a critical need for extraction, integration and management tools for information discovery and synthesis from these heterogeneous data. RESULTS: In this paper, we present a general architecture, called ALFA, for information extraction and representation from diverse biological data. The ALFA architecture consists of: (i) a networked, hierarchical, hyper-graph object model for representing information from heterogeneous data sources in a standardized, structured format; and (ii) a suite of integrated, interactive software tools for information extraction and representation from diverse biological data sources. As part of our research efforts to explore this space, we have currently prototyped the ALFA object model and a set of interactive software tools for searching, filtering, and extracting information from scientific text. In particular, we describe BioFerret, a meta-search tool for searching and filtering relevant information from the web, and ALFA Text Viewer, an interactive tool for user-guided extraction, disambiguation, and representation of information from scientific text. We further demonstrate the potential of our tools in integrating the extracted information with experimental data and diagrammatic biological models via the common underlying ALFA representation. CONTACT: aditya_vailaya@agilent.com.     

高等植物中的磷酸烯醇式丙酮酸羧激酶

简要介绍了近年来有关高等植物中磷酸烯醇式丙酮酸羧激酶（ＰＥＰＣＫ）的研究进展,并讨论了此酶的结构、功能和调节等方面的问题。     

Epidemiology of training injuries in amateur taekwondo athletes: a retrospective cohort study

The objectives of this study were to estimate the incidence and describe the pattern and severity of training injuries in taekwondo, and to compare pattern and severity of training injuries with competition injuries. One hundred and fifty-two active Australian amateur taekwondo athletes, aged 12 years or over, completed an online survey comprising questions on training exposure and injury history over the preceding 12 months. The main outcome measures were: overall injury incidence rate per athlete-year; training injury incidence rate per athlete-year, per 1000 athlete-training-sessions, and per 1000 athlete-hours of training; injury severity; and injury proportions by anatomical region and by type of injury. Injury incidence rates were calculated with 95% confidence intervals using standard methods, while injury proportions were compared using Fisher''s exact test. The vast majority (81.5%) of taekwondo injuries in an average athlete-year occurred during training. The training injury incidence rate was estimated to be 1.6 (95% CI: 1.4, 1.9) per athlete-year, 11.8 (95% CI: 10.4, 13.4) per 1000 athlete-training-sessions, and 7.0 (95% CI: 6.1, 7.9) per 1000 athlete-hours of training. Among athletes with five or fewer injuries, the severity and injury pattern of training injuries were, by and large, the same as for competition injuries. Approximately sixty percent (60.3%) of training injuries required treatment by a health professional. Considering the burden of training injuries exceeds that of competition injuries, taekwondo governing bodies and stakeholders are encouraged to devote more efforts towards the identification of risk factors for, and prevention of, training injuries in the sport of taekwondo.