Engineering the acceptor substrate specificity in the xyloglucan endotransglycosylase TmXET6.3 from nasturtium seeds (Tropaeolum majus L.)

Plant Molecular Biology - The knowledge of substrate specificity of XET enzymes is important for the general understanding of metabolic pathways to challenge the established notion that these...     

林奈收藏的欧洲蝴蝶模式标本(鳞翅目:锤角亚目)

修订了林奈(C.Linnaeus)建立的欧洲蝴蝶原始模式标本的地位.确认了38个分类单元的选模地位.本文为以下分类单元指定了选模:Papilio apollo Linnaeus,1758;P.daplidice Linnaeus,1758和P.palaeno Linnaeus,1761.对以下18个物种,由于它们在林奈...     

Point amino acid substitutions in the Ca2+-binding centers of recoverin. I. Mechanism of successive filling of Ca2+-binding centers

The molecule of photoreceptor Ca(2+)-binding protein recoverin contains four potential Ca(2+)-binding sites of the EF-hand type, but only two of them (the second and the third) can actually bind calcium ions. We studied the interaction of Ca2+ with recoverin and its mutant forms containing point amino acid substitutions at the working Ca(2+)-binding sites by measuring the intrinsic protein fluorescence and found that the substitution of Gln for Glu residues chelating Ca2+ in one (the second or the third) or simultaneously in both (the second and the third) Ca(2+)-binding sites changes the affinity of the protein to Ca2+ ions in different ways. The Gln for Glu121 substitution in the third site and the simultaneous Gln substitutions in the second (for Glu85) and in the third (for Glu121) sites result in the complete loss of the capability of recoverin for a strong binding of Ca(2+)-ions. On the other hand, the Gln for Glu85 substitution only in the second site moderately affects its affinity to the cation. Hence, we assumed that recoverin successively binds Ca(2+)-ions: the second site is filled with the cation only after the third site has been filled. The binding constants for the third and the second Ca(2+)-binding sites of recoverin determined by spectrofluorimetric titration are 3.7 x 10(6) and 3.1 x 10(5) M-1, respectively.     

Effect of L-lysine-alpha-oxidase on skin carcinoma induced by methylcholanthrene in mice]

Effect of enzyme L-lisyne-a-oxidase in complex with gel (Sakap) on carcinoma of the skin of mice induced by methylcholantrene was studied. Gel application once daily during 3 weeks decreased carcinoma dimensions on 40 per cent.     

Cultivation of Mycobacterium tuberculosis in cell culture

The method of the cultivation of M .tuberculosis in cell subcultures was tested. Five consecutive passages of 2 M. tuberculosis strains were carried out with similar inoculation and cultivation conditions. Mycobacterial cells preserved their morphological characteristics in the course of all passages. The method of M. tuberculosis cultivation in subcultured cells made it possible to study of the physiology of M. tuberculosis under conditions, most approximated to the natural tuberculosis infection in humans.     

Isolation of ginkgolides A, B, C, J and bilobalide from G. biloba extracts

Ginkgolides A, B, C and J, together with bilobalide, are unique terpenoid components of the Ginkgo biloba tree. Due to similar chemical properties, their separation is quite tedious. We have developed an efficient and rapid protocol for separation of individual ginkgolides and bilobalide from G. biloba extracts. The procedure takes advantage of enhanced susceptibility of ginkgolides B and C to benzylation and the ease of separation of these products from ginkgolides A and J which do not react. The protocol is applicable to the previously reported enriched extracts prepared from G. biloba leaves. A single chromatographic step prior to benzylation provides bilobalide and mixture of ginkgolides A, B, C, and J. After benzylation, the individual ginkgolides are separated by chromatography.     

Association of β<Subscript>2</Subscript>-microglobulin with the α<Subscript>3</Subscript> domain of H-2D<Superscript>b</Superscript> heavy chain

MHC class I molecules are heterotrimeric complexes composed of heavy chain, ₂-microglobulin (₂m) and short peptide. This trimeric complex is generated in the endoplasmic reticulum (ER), where a peptide loading complex (PLC) facilitates transport from the cytosol and binding of the peptide to the preassembled ER resident heavy chain/₂m dimers. Association of mouse MHC class I heavy chain with ₂m is characterized by allelic differences in the number and/or positions of amino acid interactions. It is unclear, however, whether all alleles follow common binding patterns with minimal contributions by allele-specific contacts, or whether essential contacts with ₂m are different for each allele. While searching for the PLC binding site in the ₃ domain of the mouse MHC class I molecule H-2D^b, we unexpectedly discovered a site critical for binding mouse, but not human, ₂m. Interestingly, amino acids in the corresponding region of another MHC class I heavy chain allele do not make contacts with the mouse ₂m. Thus, there are allelic differences in the modes of binding of ₂m to the heavy chain of MHC class I.     

Millimeter wave-induced suppression of B16 F10 melanoma growth in mice: involvement of endogenous opioids

Millimeter wave treatment (MMWT) is widely used in Eastern European countries, but is virtually unknown in Western medicine. Among reported MMWT effects is suppression of tumor growth. The main aim of the present "blind" and dosimetrically controlled experiments was to evaluate quantitatively the ability of MMWT to influence tumor growth and to assess whether endogenous opioids are involved. The murine experimental model of B16 F10 melanoma subcutaneous growth was used. MMWT characteristics were: frequency, 61.22 GHz; average incident power density, 13.3 x 10(-3) W/cm2; single exposure duration, 15 min; and exposure area, nose. Naloxone (1 mg/kg, intraperitoneally, 30 min prior to MMWT) was used as a nonspecific blocker of opioid receptors. Five daily MMW exposures, if applied starting at the fifth day following B16 melanoma cell injection, suppressed subcutaneous tumor growth. Pretreatment with naloxone completely abolished the MMWT-induced suppression of melanoma growth. The same course of 5 MMW treatments, if started on day 1 or day 10 following tumor inoculations, was ineffective. We concluded that MMWT has an anticancer therapeutic potential and that endogenous opioids are involved in MMWT-induced suppression of melanoma growth in mice. However, appropriate indications and contraindications have to be developed experimentally before recommending MMWT for clinical usage.     

Resprouting after disturbance: an experimental study with short-lived monocarpic herbs

We experimentally demonstrated the ability of three short-lived monocarpic species to vegetatively regenerate (resprout) from roots after severe disturbance. We assessed the relationship between resprouting ability and (1) timing of injury with respect to life-cycle stage (reproductive vs. vegetative plant), life-history mode (annual vs. winter annual) and phenological stage (flowering vs. fruiting plant), (2) nutrient availability, and (3) disturbance severity (removal of all axillary buds Yes/No). In a chamber experiment with the annual or potentially winter annualRorippa palustris, all injured plants resprouted in all nutrient levels and day-length regimes (day-length regimes simulated conditions of an annual and a winter annual cohort). The number of adventitious buds on roots was positively affected only by injury. The extent of regeneration and amount of regenerated biomass were higher at high nutrient level and long-day regime.