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1.
J Bello E N Granados S Lewinski H R Bello T Trueheart 《Journal of biomolecular structure & dynamics》1985,2(5):899-913
Methylated lysine, arginine and histidine residues are found in a number of proteins (for example, histones, non-histone chromosomal proteins, ribosomal proteins, calmodulin, cytochrome C, etc.). We are studying the effects of methylation on the conformations of poly(lysine) and of the effects of methylation of poly(lysine) and poly(arginine) on interactions with polynucleotides. The conformational properties of epsilon-amino-methylated poly(lysine) differ from those of unmodified poly(lysine). Methylation increases resistance to thermally-induced and NaCl-induced changes in the CD spectrum. Guanidinium chloride increases (proportional to the degree of methylation) the extent of approach to the conformation in dispute as to its being a random coil or an extended helix. Methylation enhances aggregation in the helix-inducing solvent 0.5 M Ca(ClO4)2. With increasing methylation of poly(lysine), the conformation in dodecyl sulfate changes from beta, to 50% alpha, to random coil at the maximum methylation. Increasing methylation of poly(lysine) weakens the interaction with polynucleotides in respect to dissociation by salt, linearly with methyl content. Complexes of (dAdT)n.(dAdT)n with the polypeptides are increasingly stabilized to heat denaturation by progressive methylation. However, with a series of synthetic double-stranded RNA's and DNA's a more complex situation exists, Tm increasing or decreasing, depending on the base composition, sequence and type of sugar. Methylation of poly(lysine) and poly(arginine) can have opposite effects on Tm based on results with complexes with (dI)n.(dC)n. Methylated poly(lysine) affects the CD spectrum of polynucleotides, in a manner dependent on base composition and sequence. In some cases large positive or negative psi-spectra are induced, which, in the case of (dGdC)n.(dGdC)n, can be positive or negative depending on the degree of methylation of the polypeptide and the salt concentration. It is suggested that the biological effects of methylation proteins may be evoke by salt changes in the cell cycle, and that methylation can affect local interactions with nucleic acids and larger scale structure, and interactions with lipids. 相似文献
2.
Structure-activity relationship of swainsonine. Inhibition of human alpha-mannosidases by swainsonine analogues. 总被引:1,自引:1,他引:0
I Cenci di Bello G Fleet S K Namgoong K Tadano B Winchester 《The Biochemical journal》1989,259(3):855-861
The inhibitory properties of a series of synthetic epimers and analogues of swainsonine towards the multiple forms of human alpha-mannosidases were studied in vitro and in cells in culture. Of the five epimers tested, only the 8a-epimer and 8,8a-diepimer of swainsonine were specific and competitive inhibitors (Ki values of 7.5 x 10(-5) and 2 x 10(-6) M respectively) of lysosomal alpha-mannosidases in vitro and induced storage of mannose-rich oligosaccharides in human fibroblasts in culture. The structures of these storage products indicated that processing alpha-mannosidases had also been inhibited. This was consistent with the observed inhibition in vitro of these enzymes by these compounds. In contrast, the 8-epimer, 1,8-diepimer and 2,8a-diepimer of swainsonine had no appreciable effect on any alpha-mannosidases. The corresponding open-chain analogues of swainsonine, namely 1,4-dideoxy-1,4-imino-D-mannitol, of the 8a-epimer, namely 1,4-dideoxy-1,4-imino-D-talitol, and of the 8,8a-diepimer, namely 1,4-dideoxy-1,4-imino-L-allitol, were weaker competitive inhibitors of lysosomal alpha-mannosidase, with Ki values of 1.3 x 10(-5), 1.2 x 10(-4) and 1.2 x 10(-4) M respectively. These analogues also proved less effective at inducing oligosaccharide accumulation and in disturbing glycoprotein processing. These compounds offer the opportunity to determine which alterations in the chirality of the swainsonine molecule affect its inhibitory specificity. A comparison of their biological activities has identified reagents that will be useful for studying steps in the biosynthesis and catabolism of glycoproteins and that may be of potential value in chemotherapy. 相似文献
3.
C Di Bello L Gozzini M Tonellato M G Corradini G D'Auria L Paolillo E Trivellone 《Biopolymers》1989,28(1):421-440
The proton nmr characterization of bombesin (BBS) and of two peptide fragments corresponding to the (1-6) and (6-14) sequences has been carried out at 500 MHz in dimethyl sulfoxide (DMSO-d6) using two-dimensional (2D) homo and 1H-13C heterocorrelated techniques. All resonances in the nmr spectra have been assigned and several coupling constants have been measured. The backbone J alpha CH-NH coupling constants are quite similar and around 7.8-8.2 Hz, pointing to an unfolded structure in DMSO-d6. The possibility of secondary structures in highly viscous mixtures of DMSO-d6-water was investigated. The existence of sequential nuclear Overhauser enhancement (NOE) effects in the C-terminal nonapeptide section may indicate a preferential site for secondary structuring. 相似文献
4.
Maria Di Bello Valeria Lucchini Stefania Chiari Roberto Colleoni Nicoletta Colombo Alberto Mantovani Paola Allavena 《Cancer immunology, immunotherapy : CII》1988,27(1):63-68
Summary Expression of HLA-DR antigens by purified preparations of human ovarian carcinoma cells freshly isolated from surgical specimens was examined in parallel with the capacity of tumor cells to elicit a blastogenic response from autologous lymphocytes in mixed lymphocyte-tumor culture (MLTC) assay. Of 21 tumor preparations, 11 (52%) reacted with monoclonal antibodies 279 and/or 949 specific for a monomorphic determinant of HLA-DR antigens, with heterogeneous positivity, ranging between 30% and 95%. In this series of patients positive MLTC occurred in 8/21 individual experiments. The HLA-DR expression was proportionally similar in tumors giving positive MLTC (4/8=50%) and negative MLTC (7/13=53%). The lack of correlation between DR expression on tumor cells and stimulatory activity in autologous MLTC and the fact that DR-negative tumors could induce lymphocyte stimulation, support the hypothesis that blastogenesis occurs upon recognition of tumor-associated antigens, different from DR molecules, possibly tumor-specific antigens. 相似文献
5.
6.
Gas holdup and overall volumetric oxygen transfer coefficient in airlift contactors 总被引:13,自引:0,他引:13
The two major types of airlift contactors, concentric-tube and external-loop, were investigated for their gas holdup (riser and downcomer) and overall mass transfer characteristics. Results obtained in batch charges of tap water and 0.15 kmol/m(3) NaCl solution are reported for external-loop airlift contactors having downcomer-to-riser cross-sectional area ratios, A(d)/A(r), ranging from 0.11 = A(d)/A(r) = 0.69 and for concentric-tube types in the range 0.13 = A(d)/A(r) = 0.56.The results are compared and contrasted for the two types of airlift contactors and also with corresponding results obtained in a bubble column (A(d)/A(r) = 0). Both the riser gas holdup, (epsilon(G))(r), and the overall volumetric mass transfer coefficient, (K(L)a(D))(T), were found to increase with increasing gas superficial velocity and the corresponding specific gassing power input, (P(G)/V(D))(T). However, at a specified power input both (epsilon(G))(r) and (K(L)a(D))(T) decreased with increasing A(d)/A(r) due to a resultant increase in circulating liquid velocity. Unifying generalized correlations for both types of airlift contactors are given for both (epsilon(G))(r) and (K(L)a(D))(T). These correlations are expected to be applicable as well to continuous-liquid flow bubble columns at comparable liquid velocities. 相似文献
7.
Replication of repeated DNA in human cells 总被引:1,自引:0,他引:1
The replication pattern of the repeated sequence families of human DNA has been studied by means of DNA reassociation curves. Early- and late-replicating DNA fractions were obtained from synchronized cultures of KB cells by labeling cells with bromodeoxyuridine (BUdR) early or late in the DNA synthesis period and isolating the BUdR-containing DNA by CsCl density-gradient centrifugation. Highly repeated and moderately repeated sequence classes labeled with either early or late in the DNA synthesis period were also prepared. The effect of the isolated early- or late-replicating BUdR-DNA on the rate of reassociation of the repeated sequences was then tested. Increasing concentrations of early- or late-replicating BUdR-DNA were added to a constant amount of either early- or late-replicating repeated sequences, and the fraction of label in double-stranded DNA was determined. Analysis of the DNA reassociation curves so obtained indicates that some repeated sequence families are replicated throughout the DNA synthesis period whereas others are replicated primarily in the second half. This is true for both the highly-repeated and moderately-repeated sequence classes. 相似文献
8.
Summary A comparative study of the association of mitotic acrocentric chromosomes and acrocentric bivalents at the pachytene stage shows that at least two factors can act in the associative behaviour of these chromosomes: (1) Nor activity and (2) the presence of satellite DNA in the short arms of these chromosomes. These factors do not act with the same intensity in the two cell lines studied. In lymphocytes, Nor activity prevails, whereas satellite DNA plays the main role in the association of acrocentric chromosomes in germ cells at the pachytene stage. 相似文献
9.
García-Machorro Jazmin Mirzaeicheshmeh Elaheh Fragoso-Vázquez Manuel Jonathan Bello Martiniano Méndez-Luna David León-Cardona Alám Correa-Basurto José 《化学与生物多样性》2023,20(7):e202201077
Antiviral resistance has turned into a world concern nowadays. Influenza A H1N1 emerged as a problem at the world level due to the neuraminidase (NA) mutations. The NA mutants conferred resistance to oseltamivir and zanamivir. Several efforts were conducted to develop better anti-influenza A H1N1 drugs. Our research group combined in silico methods to create a compound derived from oseltamivir to be tested in vitro against influenza A H1N1. Here we show the results of a new compound derived from oseltamivir but with specific chemical modifications, with significant affinity either on NA (in silico and in vitro assays) or HA (in silico) from influenza A H1N1 strain. We include docking and molecular dynamics (MD) simulations of the oseltamivir derivative at the binding site onto NA and HA of influenza A H1N1. Additionally, the biological experimental results show that oseltamivir derivative decreases the lytic-plaque formation on viral susceptibility assays, and it does not show cytotoxicity. Finally, oseltamivir derivative assayed on viral NA showed a concentration-dependent inhibition behavior at nM, depicting a high affinity of the compound for the enzyme, corroborated with the MD simulations results, placing our designed oseltamivir derivative as a potential antiviral against influenza A H1N1. 相似文献
10.
Importance of neurophysin dimer and of tyrosine-49 in the binding of neurohypophyseal peptides 总被引:1,自引:0,他引:1
P Nicolas J Wolff M Camier C Di Bello P Cohen 《The Journal of biological chemistry》1978,253(8):2633-2639