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Dissection of functional domains in phage fd adsorption protein. Discrimination between attachment and penetration sites 总被引:10,自引:0,他引:10
We constructed a set of deletion mutants in the attachment protein of phage fd. These mutants lack sequences coding for sections in the amino-terminal half. All the mutants that comprise a leader sequence are incorporated into phage particles. Our data strongly suggest a bipartite organization of the amino-terminal domain with (1) a region for receptor recognition and (2) a region that is necessary for penetration of the DNA into the host cell. These regions were mapped. Some evidence suggesting different roles for gene 3 protein in penetration of the outer and inner membrane are discussed. We demonstrate that the phenotypes caused by gene 3 protein in host cells can be subdivided into two groups with different sequence requirements: (1) phenotypes related to outer membrane disturbance; and (2) phenotypes related to the tolQRA transport system. 相似文献
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Sefa Celik Ali Tugrul Albayrak Sevim Akyuz Aysen E. Ozel 《Journal of biomolecular structure & dynamics》2019,37(10):2515-2526
CLTOAB is an ammonium-based ionic liquid composed of ε-Caprolactam (CL) C6H11NO and tetraoctylammonium bromide (TOAB) (C32H68BrN). In this study, experimental IR and Raman spectra of CLTOAB ionic liquid together with the computational results of the compound have been reported. The optimized geometry, vibrational frequencies, IR intensities and Raman activities of the CLTOAB were calculated using the wb97xd and B3LYP density functional methods combined with the 6-31G(d,p) basis set using Gaussian 03 program. The complete assignment of the bands was performed based on the potential energy distributions (PED%). The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The Gauge-including atomic orbital 1H-NMR and 13C-NMR chemical shifts calculations were carried out and compared with the experimental data. Furthermore to evaluate interaction between CLTOAB and DNA, molecular docking study was carried out.
Communicated by Ramaswamy H. Sarma 相似文献
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Physiological bases of genetic differences in cannibalism behavior of the confused flour beetle Tribolium confusum 总被引:2,自引:0,他引:2
Giray T Luyten YA MacPherson M Stevens L 《Evolution; international journal of organic evolution》2001,55(4):797-806
Physiological causes of genetic differences in cannibalism were examined to gain a better understanding of constraints on behavior evolution. Cannibalism has complex population level consequences in Tribolium confusum, including dramatic effects on population size. Laboratory strains with low and high cannibalism rates, obtained through inbreeding, have maintained distinct levels of cannibalism for over two decades even in the absence of artificial selection to maintain the differences. Why strains differ in their cannibalism rates was examined by measuring: (1) the nutritional benefit from cannibalism in both nutritionally good and poor environments, and (2) the possibility that eggs are an important source of water. How strains achieve differences in cannibalism was examined by testing for differences between strains in their ability to find eggs and in their tendency to eat eggs. Beetles from both strains survive equally well in a nutritionally good environment, but they accomplish this in different ways. The low cannibalism strain has high survivorship with and without cannibalism. The high cannibalism strain has low survivorship when not fed eggs and survivorship equivalent to the low cannibalism strain when fed eggs, suggesting it compensates for poor nutritional adaptation by eating eggs. The strains also differ in feeding behavior; beetles from the high cannibalism strain have a higher appetite for eggs. Beetles from the two strains did not differ in locomotor activity, search efficiency, or need for water. The observed behavioral and nutritional differences may contribute to the maintenance of different levels of cannibalism. 相似文献
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Oxidative DNA base damage, antioxidant enzyme activities and selenium status in highly iodine-deficient goitrous children 总被引:3,自引:0,他引:3
The objective of this study was to investigate oxidative DNA damage, and the levels of antioxidant enzymes (AOE) and selenium (Se) in relation to iodine deficiency and/or goiter in children. The study was performed in a group of goitrous high school children (15-18 years of age) ( n =14) with severe or moderate iodine deficiency. Thyroid hormones (TSH, FT 4 , TT 4 , FT 3 , TT 3 ), urinary iodine (UI) and plasma Se levels, and erythrocyte glutathione peroxidase (GSHPx), superoxide dismutase (SOD) and catalase (CAT) activities were determined and compared with those of a control group consisting of non-goitrous high school children ( n =14) with normal UI levels or mild iodine deficiency. In the goitrous group, concentrations of FT 4 , TT 4 , plasma Se and UI, and activities of GSHPx and SOD were found to be significantly lower. Six typical hydroxyl radical-induced base lesions in genomic DNA of peripheral blood were identified and quantified by gas chromatography/isotope-dilution mass spectrometry (GC/IDMS), and higher levels of DNA base lesions were observed in the goitrous group. The results suggest that highly iodine-deficient goitrous children may be under oxidative stress, which may lead to greater level of oxidative damage to DNA. This study supports the evidence for the reported relationship between iodine deficiency and the increased incidence of thyroid malignancies. 相似文献
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The prevalence of extended-spectrum beta-lactamase (ESBL) production by 194 nosocomial isolates of Enterobacteriacea recovered from 1995 to 1999 was investigated. The ESBL production was determined by the double-disk synergy test and was confirmed by the E-test ESBL strip. Twenty-three isolates (21 Klebsiella pneumoniae, one Escherichia coli, one Providencia rettgeri) were found as ESBL-producers (11.8%). These isolates were also usually resistant to non-betalactam antibiotics. Most of them contained a beta-lactamase with a pI of 7.6. All the strains conjugally transferred their ESBLs to recipient E. coli. Contrary to others, ESBL-producing K. pneumoniae strains isolated in 1999 were resistant to ciprofloxacin, and had the identical plasmid profiles suggestive of an outbreak. Ciprofloxacin resistance in these strains could not be transferred. In conclusion, K. pneumoniae was the main ESBL-producing species among nosocomial isolates of Enterobacteriacae in our hospital. 相似文献
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In this study, a new Pirkle‐type chiral column stationary phase for resolution of β‐methylphenylethyl amine was described by using activated Sepharose 4B as a matrix, L ‐tyrosine as a spacer arm, and an aromatic amine derivative of L ‐glutamic acid as a ligand. The binding capacities of the stationary phase were determined at different pH values (pH = 6, 7, and 8) using buffer solutions as mobile phase, and enantiomeric excess (ee) was determined by HPLC equipped with chiral column. The ee was found to be 47%. Chirality, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
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Enantioseparation of Mandelic Acid Enantiomers With Magnetic Nano‐Sorbent Modified by a Chiral Selector 下载免费PDF全文
In this study, R(+)‐α‐methylbenzylamine‐modified magnetic chiral sorbent was synthesized and assessed as a new enantioselective solid phase sorbent for separation of mandelic acid enantiomers from aqueous solutions. The chemical structures and magnetic properties of the new sorbent were characterized by vibrating sample magnetometry, transmission electron microscopy, Fourier transform infrared spectroscopy, and dynamic light scattering. The effects of different variables such as the initial concentration of racemic mandelic acid, dosage of sorbent, and contact time upon sorption characteristics of mandelic acid enantiomers on magnetic chiral sorbent were investigated. The sorption of mandelic acid enantiomers followed a pseudo‐second‐order reaction and equilibrium experiments were well fitted to a Langmuir isotherm model. The maximum adsorption capacity of racemic mandelic acid on to the magnetic chiral sorbent was found to be 405 mg g?1. The magnetic chiral sorbent has a greater affinity for (S)‐(+)‐mandelic acid compared to (R)‐(?)‐mandelic acid. The optimum resolution was achieved with 10 mL 30 mM of racemic mandelic acid and 110 mg of magnetic chiral sorbent. The best percent enantiomeric excess values (up to 64%) were obtained by use of a chiralpak AD‐H column. Chirality 27:835–842, 2015. © 2015 Wiley Periodicals, Inc. 相似文献