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1.
T. E. Samatadze A. V. Amosova S. N. Suslina T. N. Zagumennikova A. N. Tsitsilin V. A. Bykov A. V. Zelenin O. V. Muravenko 《Biology Bulletin》2012,39(6):515-524
Using a set of methods (C-banding, DAPI-staining, fluorescence hybridization in situ (FISH) with probes of 26S and 5S rDNA, and analysis of meiosis), the first comparative cytogenetic study of three species of Macleaya, producers of complex isoquinoline alkaloids, cordate Macleaya cordata (Willd.) R. Br. (2n = 20), small-fruited Macleaya microcarpa (Maxim.) Fedde (2n = 20) and Macleaya kewensis Turrill (2n = 20), was first carried out. On the basis of morphometric analysis, formulas of karyotypes were made for each species. Species ideograms for M. cordata, M. microcarpa, and M. kewensis were constructed taking into account the polymorphic variants of the C-banding patterns and indicating the location of 26S and 5S rDNA sites. A comparative study revealed that the karyotypes of M. microcarpa and M. kewensis have more in common with each other than with M. cordata. Analysis of meiotic chromosomes suggests of genetic stability of Macleaya genomes. The results of chromosome analysis were used to confirm the close relationship of Macleaya and to clarify their phylogenetic relationships. 相似文献
2.
Hiroyuki Nishimura Junya Mizutani 《Bioscience, biotechnology, and biochemistry》2013,77(11):2245-2246
A thermosensitive uracil requiring mutant of Bacillus subtilis Marburg 168 thy trp2 ts42 was examined as to the colony forming ability at the permissive and nonpermissive temperatures. The viability of the mutant cells decreased rapidly at the restrictive temperature in the modified Woese’s (MW) medium. However, the cells retained viability when sodium succinate or potassium chloride was added to the medium at that temperature although uracil deficiency was unchanged. A little but significant incorporation of adenine-8-14C into RNA still continued even after the incorporation of N-acetyl-3H-d-glucosamine into acid insoluble fraction of the cells terminated in the MW medium at 48°C. Both incorporations as well as increase of absorbance were slowed down in the presence of sodium succinate at 48°C. This mutant, ts42, was more sensitive to deoxycholate (DOC) than the parent strain. The restoration of colony forming ability after the temperature shift back from 48 to 37°C was suppressed by the addition of DOC to the medium. However, the cell became resistant to DOC when uracil was added to the medium prior to the temperature shift. 相似文献
3.
Catherine T. Kelly Bernadette S. Collins William N. Fogarty Evelyn M. Doyle 《Applied microbiology and biotechnology》1993,39(4-5):599-603
The -amylase of Micromonospora melanosporea was produced extracellularly during batch fermentation in a 5.0-1 fermentor. The absence of an organic nitrogen source in its growth medium facilitated subsequent purification of the enzyme by ammonium sulphate fractionation and two consecutive Superose-12 gel-filtration steps. The enzyme exhibited maxima for activity at pH 7.0 and 55° C and was 72% stable at pH 6.0–12.0 for 30 min at 40° C. It had a relative molecular mass of 45 000 and an isoelectric point at pH 7.6. The enzyme catalyses the conversion of starch to maltose (53%, w/w) as the predominant final end-product. Initial hydrolysis of this substrate, however, gave rise to the formation of maltooligosaccharides in the range maltotriose to maltohexaose. Maximum yields of these intermediate sugars accumulated to between 31 and 42% (w/w) as the reaction proceeded. The action of the M. melanosporea amylase on high concentrations of saccharides larger than maltotriose resulted in the formation of mainly maltose and maltotriose without concomitant glucose production. A combination of hydrolytic and transfer events is postulated to be responsible for this phenomenon and for the high maltose levels achieved.
Correspondence to: C. T. Kelly 相似文献
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The Gō-like models of proteins are constructed based on the knowledge of the native conformation. However, there are many possible choices of a Hamiltonian for which the ground state coincides with the native state. Here, we propose to use experimental data on protein stretching to determine what choices are most adequate physically. This criterion is motivated by the fact that stretching processes usually start with the native structure, in the vicinity of which the Gō-like models should work the best. Our selection procedure is applied to 62 different versions of the Gō model and is based on 28 proteins. We consider different potentials, contact maps, local stiffness energies, and energy scales—uniform and nonuniform. In the latter case, the strength of the nonuniformity was governed either by specificity or by properties related to positioning of the side groups. Among them is the simplest variant: uniform couplings with no i, i + 2 contacts. This choice also leads to good folding properties in most cases. We elucidate relationship between the local stiffness described by a potential which involves local chirality and the one which involves dihedral and bond angles. The latter stiffness improves folding but there is little difference between them when it comes to stretching. 相似文献
6.
《Phytochemistry》1987,26(5):1299-1300
The effect ofpH on Km and Vmax values of coconut α-galactosidase indicates the involvement of two ionizing groups with pKa values of 3.5 and 6.5 in catalysis. Chemical modification has indicated the presence of two carboxyl groups, a tryptophan and a tyrosine, at or near the active site of α-galactosidase. Based on these facts a new mechanism of action for α-galactosidase is proposed in which the ionizing group with a pKa of 3.5 is a carboxyl group involved in stabilizing a carbonium ion intermediate and the ionizing group with a pKa of 6.5 is a carboxyl group perturbed due to the presence of a hydrophobic residues in its vicinity which donates a H+ ion in catalysis. 相似文献
7.
The complementary fragments of human Hb α, α1–30, and α31–141 are spliced together by V8 protease in the presence of 30%n-propanol to generate the full-length molecule (Hb α-semisynthetic reaction). Unlike the other protease-catalyzed protein/peptide
splicing reactions of fragment complementing systems, the enzymic condensation of nonassociating segments of Hb α is facilitated
by the organic cosolvent induced α-helical conformation of product acting as the “molecular trap” of the splicing reaction.
The segments α24–30 and α31–40 are the shortest complementary segments that can be spliced by V8 protease. In the present study, the chemistry of the contiguous
segment (product) α24–40 has been manipulated by engineering the amino acid replacements to the positions α27 and α31 to delineate the structural basis of the molecular trap. The location of Glu27 and Arg31 residues in the contiguous segment α24–40 (as well as in other larger segments) is ideal to generate (i, i+4) side-chain carboxylate-guanidino interaction in its α-helical conformation. The amino acid residue replacement studies
have confirmed that the side chains at α27 and α31 facilitate the semisynthetic reaction. The relative influence of the substitute at these sites on the splicing reaction depends
on the chemical nature of the side chain and the location. The γ-carboxylate guanidino side-chain interaction appears to contribute
up to a maximum of 85% of the thermodynamic stability of the molecular trap. The studies also demonstrate that the thermodynamic
stability of the molecular trap is determined by two interdependent conformational aspects of the peptide. One is an amino
acid-sequence-specific event that facilitates the induction of an α-helical conformation to the contiguous segment in the
presence of organic cosolvent that imparts some amount of protease resistance to Glu30-Arg31 peptide bond. The second structural aspect is a site-specific event, ani, i+4 side-chain interaction in the α-helical conformation of the peptide which imparts an additional thermodynamic stability
to the molecular trap. The results suggest that conformationally driven “molecular traps” of protease-mediated ligation reactions
of peptides could be designed into products to facilitate the modular assembly of peptides/proteins. 相似文献
8.
V. A. Ivanisenko P. S. Demenkov S. S. Pintus T. V. Ivanisenko N. L. Podkolodny L. N. Ivanisenko A. S. Rozanov A. V. Bryanskaya E. S. Kostrjukova S. A. Levizkiy O. V. Selezneva M. M. Chukin A. K. Larin I. G. Kondratov V. N. Lazarev S. E. Peltek V. M. Govorun N. A. Kolchanov 《Doklady. Biochemistry and biophysics》2012,443(1):76-80
9.
Serova OV Popova NV Petrenko AG Deyev IE 《Biochemical and biophysical research communications》2010,402(4):658-662
CIRL-1 also called latrophilin 1 or CL belongs to the family of adhesion G protein-coupled receptors (GPCRs). As all members of adhesion GPSR family CIRL-1 consists of two heterologous subunits, extracellular hydrophilic p120 and heptahelical membrane protein p85. Both CIRL-1 subunits are encoded by one gene but as a result of intracellular proteolysis of precursor, mature receptor has two-subunit structure. It was also shown that a minor portion of the CIRL-1 receptor complexes dissociates, producing the soluble receptor ectodomain, and this dissociation is due to the second cleavage at the site between the site of primary proteolysis and the first transmembrane domain. Recently model of independent localization p120 and p85 on the cell surface was proposed. In this article we evaluated the amount of p120-p85 complex still presented on the cellular membrane and confirmed that on cell surface major amount of mature CIRL-1 presented as a p120-p85 subunit complex. 相似文献
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The kinetics of renaturation of the β2-subunit of Escherichia coli tryptophan-synthetase (l-serine hydrolyase (adding indole) E.C. 4.2.1.20) and those of its two proteolytic fragments F1 and F2 are studied and compared. Steps corresponding to the refolding of F1, to the association of the folded F1 and F2 fragments, and to an isomerization of the associated protein are identified. These steps are ordered on the pathway of renaturation and some of their kinetic parameters are determined. This leads to a tentative kinetic model for the renaturation of nicked-β2 starting from the denatured F1 and F2 fragments.The step corresponding to the refolding of the F1 domain, as well as that corresponding to the last rate-limiting isomerization leading to the native protein, is shown to be the same in the refolding of the entire, uncleaved β2-protein. It is concluded that the refolded F1 fragment corresponds to a folding intermediate on the pathway of renaturation of the β2-subunit. 相似文献
12.
ObjectiveMost of the studies about trapeziometacarpal joint assume that it exhibits only two independent degrees of freedom, but the experimental or theoretical support for considering a two-degrees of freedom model is not always clear.Materials and methodsTherefore, an in vitro kinematic study has been designed to demonstrate, from experimental data, that only two of the trapeziometacarpal degrees of freedom (i.e., flexion/extension and adduction/abduction) are non-null and independent. Several movements of maximal amplitude in flexion, abduction and circumduction have been realized and the relative position and orientation of the segment coordinate system embedded on the first metacarpal with respect to that embedded on the trapezium have been collected using electromagnetic sensors. The trapeziometacarpal rotations have been described using a joint coordinate system and the joint displacements have been evaluated on the axes of this coordinate system.ResultsThe root mean square (RMS) values of the joint displacement components have been found small enough to assume that the trapeziometacarpal joint has no translation degrees of freedom. A paraboloid coupling equation has been found between the internal/external rotation angle and the two other, flexion/extension and adduction/abduction, angles.ConclusionThus, this study demonstrates that the trapeziometacarpal joint has only two independent rotational degrees of freedom, and further, the described methodology could also be used to determine the coupling laws between degrees of freedom of various joints. 相似文献
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(1) Mixed bile salt micelle solubilized either cholesterol or β-sitosterol to a comparable extent. When added simultaneously, β-sitosterol restricted the micellar solubility of cholesterol. (2) β-Sitosterol also reduced the cholesterol content in the aqueous (micellar) phase of the intestinal contents of rats, the extent of reduction being comparable with that observed in vitro. The intestinal uptake of cholesterol in vivo was equivalent to the micellar incorporation of cholesterol both in vitro and in vivo. (3) β-Sitosterol had no inhibitory effect on cholesterol absorption from the micellar solution in jejunal loops in situ, whereas the rate of β-sitosterol uptake was only about one-fifth that of cholesterol. (4) The intestinal uptake of β-sitosterol intubated into the stomach of rats was about one-fifth that of cholesterol. The intestinal brush-border membrane discriminated these sterols. These results suggest that the restriction of the micellar solubility of cholesterol, rather than the inhibition of uptake from brush-border membrane, is the major determinant for the interference of β-sitosterol with cholesterol absorption. 相似文献
15.
The study aimed at examining the diagnostic utility of the Impact of Event Scale-Revised (IES-R) as a screening tool for post-traumatic stress disorder (PTSD) in survivors of war. The IES-R was completed by two independent samples that had survived the war in the Balkans: a sample of randomly selected people who had stayed in the area of former conflict (n = 3,313) and a sample of refugees to Western European countries (n = 854). PTSD was diagnosed using the MINI International Neuropsychiatric Interview. Prevalence of PTSD was 20.1% in the Balkan sample and 33.1% in the refugee sample. Results revealed that when considering a minimum value of specificity of 0.80, the optimally sensitive cut-off score for screening for PTSD in the Balkan sample was 34. In both the Balkan sample and the refugee sample, this cut-off score provided good values on sensitivity (0.86 and 0.89, respectively) and overall efficiency (0.81 and 0.79, respectively). Further, the kappa coefficients for sensitivity for the cut-off of 34 were 0.80 in both samples. Findings of this study support the clinical utility of the IES-R as a screening tool for PTSD in large-scale research studies and intervention studies if structured diagnostic interviews are regarded as too labor-intensive and too costly. 相似文献
16.
《The International journal of biochemistry》1994,26(8):971-976
- 1.1. The α-I fragment of human spectrin that carries the binding site on the α-chain of spectrin for the β -chain has been purified from limited trypsin digests of spectrin by means of FPLC.
- 2.2. The self-association of spectrin and the binding of the α-I fragment to spectrin heterodimers and to tetramers have been quantified through the use of gel electrophoresis, staining with Coomassie Blue, and quantification of the bound dye following elution with pyridine.
- 3.3. The parameters of self-association were found to be consistent with those estimated from sedimentation equilibrium analysis.
- 4.4. The data were consistent with a model in which both self-association and the binding of the α-I fragment are considered to occur through an intermediate in which the α-β interface is initially dissociated. The α-β interface in the heterodimer was found to be less stable than that of higher oligomers by approx. 3 kJ/mol.
17.
Staphylococcus aureus spreads on the surface of soft agar, a phenomenon we termed "colony spreading." Here, we found that S. aureus culture supernatant inhibited colony spreading. We purified δ-hemolysin (Hld, δ-toxin), a major protein secreted from S. aureus, as a compound that inhibits colony spreading. The culture supernatants of hld-disrupted mutants had 30-fold lower colony-spreading inhibitory activity than those of the parent strain. Furthermore, hld-disrupted mutants had higher colony-spreading ability than the parent strain. These results suggest that S. aureus negatively regulates colony spreading by secreting δ-hemolysin. 相似文献
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19.
Siegfried Fritzsche Martin Gaub Reinhold Haberlandt Gerd Hofmann 《Journal of molecular modeling》1996,2(9):286-292
Using molecular dynamical computer simulations (MD) the dynamics of kinetic processes in zeolites will be discussed on a molecular level. Small changes in lattice parameters can cause dramatical changes in the diffusion coefficient. The presence of cations Na+, Ca2+ also strongly influences the diffusion. Changes of the self-diffusivities will be discussed that appear if a vibrating lattice instead of a rigid one is used. Nonequilibrium simulations show the correlation between transport-diffusion and self-diffusion in zeolites. 相似文献
20.
A carotenoid requirement for photosystem I activity in spinach chloroplasts using extraction-reconstitution technique has been investigated. The transfer of electron from N,N,N,N-tetramethyl-p-phenylene diamine through the chloroplast photosystem to methyl viologen dye or to NADP+ was used as an assay of photosystem I activity. Extraction of lyophilized spinach chloroplasts with heptane at near 0°C removed almost all -carotene and reduced photochemical activities associated with photosystem I to a low level (about 15% of the original activity). Reconstitution of the extracted chloroplasts with -carotene completely restored photosystem I activity. The maximum rate of methyl viologen photoreduction in reconstituted chloroplasts occurred at an -carotene/chlorophyll molar ratio of 0.5. Cyclic phosphorylation mediated by phenazine methosulphate was partially restored. Xanthophylls (lutein, neoxanthin, violaxanthin), as components of chloroplast membranes, were not able to replace -carotene in reconstitution of chloroplasts and had essentially no effect on restoring photoreactions. On the basis of the P700/total chlorophyll ratio it can be assumed that extraction of lyophilized chloroplasts with heptane do not affect photosystem I reaction centre. Therefore it is possible that -carotene, removed during heptane extraction and belonging mainly to the antenna pigment pool of photosystem I, is effective in the restoration of photosystem I activity.Abbreviations chl
chlorophyll
- DCIP
2,6-dichlorophenolindophenol
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- EPR
electron paramagnetic resonance
- MV
methyl viologen
- PMS
phenazine methosulphate
- PQA
plastoquinone A
- PS I
photosystem I
- PS II
photosystem II
- TMPD
N,N,N',N'-tetramethyl-p-phenylene diamine
- Tricine
N-tris(hydroxymethyl)methyglycine. D-1, D-10, D-50, D-144 represent chloroplast subfractions sedimented at 1000 × g, 10,000 g, 50,000 × g and 144,000 × g
- s
supernatant
This paper is a partial fulfillment of the requirements for the Ph.D. degree of A.T. at Maria Curie-Skodowska University, Lublin. 相似文献