排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
Xianyang Fang Jinbu Wang Ina P. O’Carroll Michelle Mitchell Xiaobing Zuo Yi Wang Ping Yu Yu Liu Jason W. Rausch Marzena A. Dyba Jørgen Kjems Charles D. Schwieters Soenke Seifert Randall E. Winans Norman R. Watts Stephen J. Stahl Paul T. Wingfield R. Andrew Byrd Stuart F.J. Le Grice Alan Rein Yun-Xing Wang 《Cell》2013
2.
Conformational preferences of Ac-deltaAla-NMe2 and Ac-(Z)-deltaPhe-NMe2 were studied and compared with those of their monomethyl counterparts as well as with those of their saturated analogues. X-Ray data and energy calculations revealed a highly conservative conformation of the dehydro dimethylamides, which is located in a high-energy region of the Ramachandran map. 相似文献
3.
Kwiecień RA Rostkowski M Dybała-Defratyka A Paneth P 《Journal of inorganic biochemistry》2004,98(6):1078-1086
Several semiempirical methods (MNDO-d, PM3tm, PM3-d, PM5, PM6, and AM1-d) have been tested against experimental data and density functional theory (DFT) results in search for the best methods that can be used for quantum-mechanical-molecular mechanics (QM/MM) modeling of corrinoid systems of vitamin B(12) co-factor. It has been found that the PM6 parametrization in its present form gives results closest to hybrid DFT calculations that are most widely used thus far. In comparison with pure DFT and experimental data the best agreement is obtained for PM3tm parametrization, while PM6 yields slightly worse results. AM1-d yields bad geometry of the corrin moiety. The worst performance was observed for MNDO-d, which has severe problem with position and orientation of the alpha-ligands. 相似文献
4.
We report immunofluorescence imaging with a spatial resolution well beyond the diffraction limit. An axial resolution of approximately 50 nm, corresponding to 1/16 of the irradiation wavelength of 793 nm, is achieved by stimulated emission depletion through opposing lenses. We have demonstrated not only that an antibody-tagged label is stable enough to be recorded in this microscopy mode, but also that subdiffraction resolution can be obtained using a standard immunofluorescence preparation. 相似文献
5.
Sztanke K Pasternak K Rzymowska J Sztanke M Kandefer-Szerszeń M Dybała I Kozioł AE 《Bioorganic & medicinal chemistry》2007,15(8):2837-2849
The series of 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-diones (11-20) and 8-aryl-4-imino-2,3,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazin-3(6H)-ones (21-25) were designed and their in vitro cytotoxic activities against human LS180, HeLa, T47D, A549 and RPMI 8226 carcinoma cells are presented. In the crystalline state molecule 12 exists as the predominant tautomeric 3-oxo form, whereas the second possible 3-hydroxy tautomer is not observed. Compound 19 revealed a strong affection to LS180 cancer cells at lower tested concentration (37.9 microM) and simultaneously was found to be non-toxic towards the normal cell line investigated--GMK cells. Furthermore, this compound was proved to possess the efficiency for DNA strand breakage of the examined cancer cell lines. However, imidazotriazin-3,4-dione 20 was able to cause significant viability decreases in human RPMI 8226 peripheral blood myeloma cells. Compound 22 has exhibited remarkable inhibitory effects against LS180 and A549 carcinoma cells, whereas 24 revealed the highest growth inhibition against A549 cell line. Simultaneously, at lower tested concentration these compounds were proved to be completely non-toxic for GMK cells. Moreover, cytotoxic and antibacterial properties of starting, tautomeric 1-aryl-2-hydrazonoimidazolidines (1-6 and 8-9) are presented. Six of them (1-2, 4-6 and 9) proved active as antimicrobials. All these compounds revealed MIC values in the range of 15.0-78.6 microM. Their activities were compared to those of ampicillin and chloramphenicol. 相似文献
6.
7.
Rui Gong Bang K. Vu Yang Feng DaRue A. Prieto Marzena A. Dyba Joseph D. Walsh Ponraj Prabakaran Timothy D. Veenstra Sergey G. Tarasov Rieko Ishima Dimiter S. Dimitrov 《The Journal of biological chemistry》2009,284(21):14203-14210
The immunoglobulin (Ig) constant CH2 domain is critical for antibody
effector functions. Isolated CH2 domains are promising as scaffolds for
construction of libraries containing diverse binders that could also confer
some effector functions. However, previous work has shown that an isolated
murine CH2 domain is relatively unstable to thermally induced unfolding. To
explore unfolding mechanisms of isolated human CH2 and increase its stability
γ1 CH2 was cloned and a panel of cysteine mutants was constructed. Human
γ1 CH2 unfolded at a higher temperature (Tm = 54.1
°C, as measured by circular dichroism) than that previously reported for a
mouse CH2 (41 °C). One mutant (m01) was remarkably stable
(Tm = 73.8 °C). Similar results were obtained by
differential scanning calorimetry. This mutant was also significantly more
stable than the wild-type CH2 against urea induced unfolding (50% unfolding at
urea concentration of 6.8 m versus 4.2 m). The
m01 was highly soluble and monomeric. The existence of the second disulfide
bond in m01 and its correct position were demonstrated by mass spectrometry
and nuclear magnetic resonance spectroscopy, respectively. The loops were on
average more flexible than the framework in both CH2 and m01, and the overall
secondary structure was not affected by the additional disulfide bond. These
data suggest that a human CH2 domain is relatively stable to unfolding at
physiological temperature, and that both CH2 and the highly stable mutant m01
are promising new scaffolds for the development of therapeutics against human
diseases.Monoclonal antibodies
(mAbs)2 with high
affinity and specificity are now well established therapeutics and invaluable
tools for biological research. It appears that their use will continue to
expand in both targets and disease indications. However, a fundamental problem
for full-size mAbs that limits their applications is their poor penetration
into tissues (e.g. solid tumors) and poor or absent binding to
regions on the surface of some molecules (e.g. on the HIV envelope
glycoprotein) that are accessible by molecules of smaller size. Antibody
fragments, e.g. Fabs (∼60 kDa) or single chain Fv fragments
(scFvs) (20∼30 kDa), are significantly smaller than full-size antibodies
(∼150 kDa), and have been used as imaging reagents and candidate
therapeutics. Even smaller fragments of antibodies are of great interest and
advantageous for pharmaceutical applications including cancer targeting and
imaging.During the last decade a large amount of work has been aimed at developing
of small size binders with scaffolds based on various highly stable human and
non-human molecules
(1–8).
A promising direction is the development of binders based on the heavy or
light chain variable region of an antibody; these fragments ranging in size
from 11 kDa to 15 kDa were called “domain antibodies” or
“dAbs” (7,
9). A unique kind of antibodies
composed only of heavy chains are naturally formed in camels, dromedaries, and
llamas, and their variable regions can also recognize antigens as single
domain fragments (10). Not
only is the overall size of the dAbs much smaller than that of full-size
antibodies but also their paratopes are concentrated over a smaller area so
that the dAbs provide the capability of interacting with novel epitopes that
are inaccessible to conventional antibodies or antibody fragments with paired
light and heavy chain variable domains.The structure of the constant antibody domains is similar to that of the
variable domains consisting of β-strands connected mostly with loops or
short helices. The second domain of the α, δ, and γ heavy
chain constant regions, CH2, is unique in that it exhibits very weak
carbohydrate-mediated interchain protein-protein interactions in contrast to
the extensive interchain interactions that occur between the other domains.
The expression of murine CH2 in bacteria, which does not support
glycosylation, results in a monomeric domain
(11). It has been hypothesized
that the CH2 domain (CH2 of IgG, IgA, and IgD, and CH3 of IgE and IgM) could
be used as a scaffold and could offer additional advantages compared with
those of dAbs because it contains binding sites or portions of binding sites
conferring effector and stability functions
(12).It was found previously that an isolated murine CH2 is relatively unstable
at physiological temperature with a temperature of 50% unfolding
(Tm) slightly higher than 37 °C
(11). We have hypothesized
that human CH2 would exhibit different stability because of significant
differences in the sequence compared with its murine counterpart. Therefore,
we have extensively characterized the stability of an isolated unglycosylated
single CH2 domain. We found that its stability is significantly higher than
the previously reported for the murine CH2. We further increased the stability
of the human CH2 by engineering an additional disulfide bond between the A and
G strands. One of the newly developed mutants, denoted as m01, exhibited
significantly higher stability (Tm = 73.8 °C) than
that of wild type CH2. We suggest that both the wild type CH2 and the newly
developed mutant, m01, could be used as scaffolds for binders. These results
also demonstrate for the first time that the stability of constant antibody
domains can be dramatically increased by engineering of an additional
disulfide bond. The increase in stability of isolated domains may result in an
increase in stability of larger antibody fragments, e.g. Fc, and
therefore could have implications as a general method for increasing antibody
stability. Thus, it appears that further development of CH2 and its more
stable variants as scaffolds could provide new opportunities for
identification of potentially useful therapeutics. 相似文献
8.
Ulrike Muus Curtis Hose Wei Yao Teresa Kosakowska-Cholody David Farnsworth Marzena Dyba George T. Lountos David S. Waugh Anne Monks Terrence R. Burke Christopher J. Michejda 《Bioorganic & medicinal chemistry》2010,18(12):4535-4541
The current paper presents the synthesis and evaluation of a series of maleimides that were designed to inhibit the Cdc25 phosphatase by alkylation of catalytically essential cysteine residues. Although in HepB3 cell culture assays the analogues did exhibit antiproliferative IC50 values ranging from sub-micromolar to greater than 100 μM, inhibition of Cdc25 through cysteine alkylation could not be demonstrated. It was also found that analysis using fluorescence activated cell sorting (FACS) following treatment with the most potent analogue (1t) did not provide data consistent with inhibition at one specific point in the cell cycle, as would be expected if Cdc25A were inhibited. Further studies with a subset of analogues resulted in a correlation of antiproliferative potencies with activation of the unfolded protein response (UPR). The UPR is a regulatory pathway that temporarily suspends protein production when misfolding of proteins occurs within the endoplastic reticulum (ER). In addition, ER chaperones that promote proper refolding become up-regulated. If cellular damage cannot be resolved by these mechanisms, then the UPR can initiate apoptosis. The current study indicates that these maleimide analogues lead to UPR activation, which is predictive of the selective antiproliferative activity of the series. 相似文献
9.
Our previous studies revealed that the nonapeptide fragment of HLA-DR molecule, located in the beta chain 164-172 with the VPRSGEVYT sequence, suppresses the immune responses. The sequence is located on the exposed molecule loop, therefore it may be involved in the interactions with other proteins. We suggested that the loop may serve as a functional epitope on the HLA class II surface for intermolecular binding, and that possible mechanism of biological action of the synthesized peptides is associated with interfering of adhesion of HLA class II molecules to their coreceptors. It has been postulated that oligomerization of the coreceptors is required for stable binding to class II HLA. Based on the crystal dimeric structure of HLA-DR molecules, we designed, and synthesized molecules able to induce the putative coreceptors dimerization. The synthesized series of compounds consisted of two VPRSGEVYT sequences linked through their C-termini by spacers of different length: (VPRSGEVYTGn)2K-NH2 ( n = 4-6). The results demonstrate that the dimerization of the nonapeptide fragment of HLA-DR results in enhanced immunosuppressory properties. 相似文献
10.
Our previous studies revealed that the nonapeptide fragment of HLA-DQ located in the beta 164-172 loop of the Thr-Pro-Gln-Arg-Gly-Asp-Val-Tyr-Thr sequence suppresses the immune humoral and cellular responses [30]. Based on the crystal structure of HLA-class II molecules we designed and synthesized a cyclic analog with restricted conformation, cyclo(Suc-Thr-Pro-Gln-Arg-Gly-Asp-Val-Lys)-Thr-OH (Suc = succinyl) by reacting a Lys side chain with a succinylated N-terminus. The cyclization product more potently suppresses the cellular immune response than its linear counterparts and is efficiently cleaved by trypsin. The results indicate that the beta 164-172 loop may serve as a functional epitope on the HLA class II surface for intermolecular binding. 相似文献