Structural changes of beta-lactoglobulin during thermal unfolding and refolding--an FT-IR and circular dichroism study.

We have quantitatively characterized by FT-IR spectroscopy the contents of secondary structure of beta-lactoglobulin during thermal unfolding and subsequent refolding. Our data clearly indicate that considerable amount of secondary structure, particularly beta-sheet, still remained intact even at 90 degrees C. Noticeable changes in secondary structure of beta-lactoglobulin were observed only above 70 degrees C. The refolded protein regained, within limits of experimental error, all of the secondary structure lost during thermal unfolding. The data also indicate that the refolding mechanism operating at pH 7.0 and 2.0 are the same. Identical secondary structure of native and refolded beta-lactoglobulin was also indicated by far-UV circular dichroic spectra of the two forms of protein. Near UV circular dichroic spectra of the same two forms showed considerable differences indicating less tertiary structure of refolded beta-lactoglobulin. The combined CD and FT-IR data indicated that refolded form of beta-lactoglobulin could be characterized as a molten globule state as it had native-like secondary structure and compromised tertiary structure.

Disturbances in cellular features and elemental homeostasis in the integument of a freshwater fish Channa punctatus (Bloch) in relation to hydrogen ion concentration of polluted water.

Scanning electron microscopy revealed that the cellular and morphological defects in the integument of Channa punctatus, associated with heavy metal and other environmental pollution was related to a significant extent to the hydrogen ion concentration of the water. At low pH, the epidermis showed severe lesions, and the scale lost its attachment with the skin, due to lepidontal alterations of the circuli. Atomic absorption spectroscopic analysis of the tissue indicated disturbances in the homeostasis of several elements, which probably played a major role in causing the cellular and morphological defects. Experimental monitoring of the pH of the polluted water to near-neutral, reduced significantly the extent of cellular and morphological defects and disturbances in elemental homeostasis.

Effect of prenatal lead toxicity on surface ultrastructural features, elemental composition and infrared absorption characteristics of the skin of albino mice.

The epidermis and dermis of albino mice born to females receiving oral sublethal doses of lead during pregnancy developed several abnormalities. These included perforations, tissue damage, cell deformity, and disordered organization of collagen bundles, as revealed by scanning electron microscopy. An increase in the concentrations of zinc, iron, magnesium, calcium and a decrease in that of copper was evident from atomic absorption spectroscopical analysis, when entire skin tissues were examined. Infrared spectroscopy revealed the occurrence of split bands in the spectra at 1,200-1,000 cm(-1), suggesting a reduction in the symmetry of the sulphate group (glycosaminoglycans) of skin probably caused by covalent bonding of it with lead.

Bupropion overdose: a potential problem with the new 'miracle' anti-smoking drug.

Bupropion (Zyban) has recently been launched in the UK as an aid to smoking cessation. As a result of the considerable publicity, there has been unprecedented demand for this new drug in primary care. Within a few weeks of its launch, four patients presented to our A&E department having taken bupropion as an intentional overdose. Three recovered with simple supportive measures; one one was critically ill and required admission to the intensive care unit. There are several case reports on bupropion overdose in the US but none so far in the UK.

Do animals bite more during a full moon? Retrospective observational analysis.

OBJECTIVE: To test the hypothesis that the incidence of animal bites increases at the time of a full moon. DESIGN: Retrospective observational analysis. SETTING: Accident and emergency department at a general hospital in an English city. SUBJECTS: 1621 consecutive patients, irrespective of age and sex. MAIN OUTCOME MEASURES: Number of patients who attended an accident and emergency department during 1997 to 1999 after being bitten by an animal. The number of bites in each day was compared with the lunar phase in each month. RESULTS: The incidence of animal bites rose significantly at the time of a full moon. With the period of the full moon as the reference period, the incidence rate ratio of the bites for all other periods of the lunar cycle was significantly lower (P <0.001). CONCLUSIONS: The full moon is associated with a significant increase in animal bites to humans.

Thermal unfolding and refolding of beta-lactoglobulin. An intrinsic andextrinsic fluorescence study.

The conformational features of beta-lactoglobulin, refolded by cooling from a thermally perturbed state, has been characterized by intrinsic and extrinsic fluorescence measurements on the protein. It is found that even at 85-90 degrees C, beta-lactoglobulin does not completely lose its folded structure. The unfolding and refolding of beta-lactoglobulin as observed through intrinsic tryptophan fluorescence is nearly reversible because the native beta-lactoglobulin and its refolded form, following heating and cooling, show nearly identical tryptophan fluorescence properties. However, the fluorescence properties of an extrinsic probe 1-anilino 8-naphthalene sulfonic acid (ANS) for the native and refolded forms are quite different from each other. Significant increase in fluorescence intensity and blue shifts in emission maxima of ANS bound to refolded beta-lactoglobulin is observed compared to that of the native form. Our results indicate that beta-lactoglobulin, refolded after heating to above 70 degrees C, has deep hydrophobic pockets which can be accessed by ANS. These pockets are either nonexistent or inaccessible to ANS in native beta-lactoglobulin. The opening of the central cavity collapses at pH close to the isoelectric pH of the protein. This indicates that electrostatic repulsion is necessary to keep this access open.

Electron microscopy and spectroscopical studies on the coloured patches on the wing of a butterfly, Graphium sarpedon (Lepidoptera: Papillionidae) with reference to their photobiological and electrical properties.

The surface ultra-structural features of the coloured patches on the wing of a butterfly Graphium sarpedon have been studied with the help of scanning electron microscopy. Comparisons have been made between the dark brown area and the light green patches of the wing. A diffraction grating pattern with 15 lines per micron 2 with a uniform spacing of about 1 micron is present in the light green patches. A slightly coarser grating is present on the dark brown area, which constitutes the major portion of the wing. Sensilla chaetica was found on both the light green and dark brown area. A special type of sensilla trichodea with a big socket and some elongated projections were localized only on the light green patches. This region of the wing also contains some spherical structures with a diameter of 0.5 to 0.6 micron. The infra-red spectroscopy has revealed some differences in the nature and position of the peaks in the low-energy region in the dark brown area and the light green patches. The atomic absorption spectroscopy also shows qualitative as well as quantitative differences in the inorganic set up of the two regions. The electron spin resonance spectroscopy reveals the presence of a peak in the dark brown region only, indicating the presence of free radical in it. The differences observed in the ultra-structural and spectroscopical features, and also in the inorganic components of the two regions, are discussed in relation to their physical and physiological properties.