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31.
It has been proposed recently that ATP hydrolysis in ATPase enzymes proceeds via an initial intermediate in which the dissociated γ-phosphate of ATP is bound in the protein as a metaphosphate (PγO3−). A combined quantum/classical analysis of this dissociated nucleotide state inside myosin provides a quantitative understanding of how the enzyme stabilizes this unusual metaphosphate. Indeed, in vacuum, the energy of the ADP3−·PγO3−·Mg2+ complex is much higher than that of the undissociated ATP4−. The protein brings it to a surprisingly low value. Energy decomposition reveals how much each interaction in the protein stabilizes the metaphosphate state; backbone peptides of the P-loop contribute 50% of the stabilization energy, and the side chain of Lys-185+ contributes 25%. This can be explained by the fact that these groups make strong favorable interactions with the α- and β-phosphates, thus favoring the charge distribution of the metaphosphate state over that of the ATP state. Further stabilization (16%) is achieved by a hydrogen bond between the backbone C=O of Ser-237 (on loop Switch-1) and a water molecule perfectly positioned to attack the PγO3− in the subsequent hydrolysis step. The planar and singly negative PγO3− is a much better target for the subsequent nucleophilic attack by a negatively charged OH− than the tetrahedral and doubly negative PγO42− group of ATP. Therefore, we argue that the present mechanism of metaphosphate stabilization is common to the large family of nucleotide-hydrolyzing enzymes. Methodologically, this work presents a computational approach that allows us to obtain a truly quantitative conception of enzymatic strategy. 相似文献
32.
33.
Sharif Moradi Parisa Torabi Saeed Mohebbi Sara Amjadian Piter Bosma Farnoush Faridbod Vahid Khoddami Morteza Hosseini Sadegh Babashah Maryam Ghotbaddini Arezoo Rasti Faezeh Shekari Hamid Sadeghi-Abandansari Jafar Kiani Mehdi Shamsara Mohammad Kazemi-Ashtiani Samira Gholami 《BioEssays : news and reviews in molecular, cellular and developmental biology》2020,42(6):2000042
34.
Iffat Chughtai 《Acta zoologica》1986,67(3):165-171
The Perkinsiana acrosome is elongated, pointed and tapering, strengthened anteriorly by cortical rings of longitudinally running units. The Pseudopotamilla acrosome is cap-like and its apical region contains a laminar body with two electron densities, the laminae crossed by occasional lines of dislocation, as in a crystal. These apparently solid regions are closely followed by peripherally situated lucent zones. The zone in Pseudopotamilla contains tubules, which are very like those in Sabella sperm, except that they lack connections with the acrosome base. Both species are probably broadcast spawners and have nuclei, mitochondria, centrioles and flagella of the primitive type. This may, however, be a secondary reversion through neoteny. 相似文献
35.
H. Asadi Rahmani N. Saleh-rastin K. Khavazi A. Asgharzadeh D. Fewer S. Kiani K. Lindström 《World journal of microbiology & biotechnology》2009,25(4):591-600
Nodulation of soybeans grown in semi-arid region of southern parts of Iran is poor due to high air and soil temperatures.
Here we identified thermotolerant isolates of soybean bradyrhizobia and evaluated the nitrogen fixation efficiency of the
isolates under heat stress conditions in greenhouse and field experiments. The ability of fifty-six bradyrhizobial isolates
to grow on solid or in liquid yeast extract mannitol medium at 38 and 41°C was evaluated. We identified 19 isolates, which
were able to grow at 38°C and 10 isolates able to grow at 41°C. Greenhouse experiments were carried out at 28 and 38°C to
study the nitrogen-fixing capacity of the isolates under optimal and high temperature conditions. Ten isolates had a symbiotic
index of effectiveness of 80% or greater compared with nitrogen-fertilized treatments in greenhouse experiments at 28°C. Some
thermotolerant isolates demonstrated good nitrogen-fixing performance at 38°C. Eight isolates were selected for use in a field
trial in the natural high temperature environment of the Dezful region in Iran. Our results demonstrate that geographical
origin can have a great influence on the successful selection of thermotolerant bradyrhizobia. Our thermotolerant isolates
were mainly obtained from high-temperature regions, and improved shoot dry matter, nitrogen-uptake and seed yield of the plants. 相似文献
36.
Farzaneh Sharifzad Hamed Yasavoli-Sharahi Saeid Mardpour Esmaeil Fakharian Hassan Nikuinejad Yasaman Heydari Soura Mardpour Adeleh Taghikhani Reza khellat Somayeh Vafaei Sahar Kiani Saeid Ghavami Marek Łos Mehdi Noureddini Marzieh Ebrahimi Javad Verdi Amir Ali Hamidieh 《Journal of cellular physiology》2019,234(12):22493-22504
Glioblastoma multiforme (GBM) is a unique aggressive tumor and mostly develops in the brain, while rarely spreading out of the central nervous system. It is associated with a high mortality rate; despite tremendous efforts having been made for effective therapy, tumor recurrence occurs with high prevalence. To elucidate the mechanisms that lead to new drug discovery, animal models of tumor progression is one of the oldest and most beneficial approaches to not only investigating the aggressive nature of the tumor, but also improving preclinical research. It is also a useful tool for predicting novel therapies' effectiveness as well as side effects. However, there are concerns that must be considered, such as the heterogeneity of tumor, biological properties, pharma dynamic, and anatomic shapes of the models, which have to be similar to humans as much as possible. Although several methods and various species have been used for this approach, the real recapitulation of the human tumor has been left under discussion. The GBM model, which has been verified in this study, has been established by using the Rat C6 cell line. By exploiting bioinformatic tools, the similarities between aberrant gene expression and pathways have been predicted. In this regard, 610 common genes and a number of pathways have been detected. Moreover, while magnetic resonance imaging analysis enables us to compare tumor features between these two specious, pathological findings provides most of the human GBM characteristics. Therefore, the present study provides genomics, pathologic, and imaging evidence for showing the similarities between human and rat GBM models. 相似文献
37.
Maryam Hatami Nargess Zare Mehrjardi Sahar Kiani Katayoun Hemmesi Hossein Azizi Abdolhossein Shahverdi Hossein Baharvand 《Cytotherapy》2009,11(5):618-630
Background aimsSeveral studies have reported functional improvement after transplantation of in vivo-derived neural progenitor cells (NPC) into injured spinal cord. However, the potential of human embryonic stem cell-derived NPC (hESC-NPC) as a tool for cell replacement of spinal cord injury (SCI) should be considered.MethodsWe report on the generation of NPC as neural-like tubes in adherent and feeder-free hESC using a defined media supplemented with growth factors, and their transplantation in collagen scaffolds in adult rats subjected to midline lateral hemisection SCI.ResultshESC-NPC were highly expressed molecular features of NPC such as Nestin, Sox1 and Pax6. Furthermore, these cells exhibited the multipotential characteristic of differentiating into neurons and glials in vitro. Implantation of xenografted hESC-NPC into the spinal cord with collagen scaffold improved the recovery of hindlimb locomotor function and sensory responses in an adult rat model of SCI. Analysis of transplanted cells showed migration toward the spinal cord and both neural and glial differentiation in vivo.ConclusionsThese findings show that transplantation of hESC-NPC in collagen scaffolds into an injured spinal cord may provide a new approach to SCI. 相似文献
38.
Density functional theory computations were carried out for 11-vertex nido-p-block-hetero(carba)boranes and -borates containing silicon, germanium, tin, arsenic, antimony, sulfur, selenium and tellurium heteroatoms. A set of quantitative values called “estimated energy penalties” was derived by comparing the energies of two reference structures that differ with respect to one structural feature only. These energy penalties behave additively, i.e., they allow us to reproduce the DFT-computed relative stabilities of 11-vertex nido-heteroboranes in general with good accuracy and to predict the thermodynamic stabilities of unknown structures easily. Energy penalties for neighboring heteroatoms (HetHet and HetHet′) decrease down the group and increase along the period (indirectly proportional to covalent radii). Energy penalties for a five- rather than four-coordinate heteroatom, [Het5k(1) and Het5k(2)], generally, increase down group 14 but decrease down group 16, while there are mixed trends for group 15 heteroatoms. The sum of HetHet′ energy penalties results in different but easily predictable open-face heteroatom positions in the thermodynamically most stable mixed heterocarbaboranes and -borates with more than two heteroatoms.
Figure Correlation of HetHet′ and HetC increments with covalent radii of group 15 heteroatoms
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday 相似文献
39.
Liu TB Fedak PW Weisel RD Yasuda T Kiani G Mickle DA Jia ZQ Li RK 《American journal of physiology. Heart and circulatory physiology》2004,287(6):H2840-H2849
The functional benefit of cell transplantation after a myocardial infarction is diminished by early cell losses. IGF-1 enhances cell proliferation and survival. We hypothesized that IGF-1-transfected smooth muscle cells (SMCs) would enhance cell survival and improve engraftment after cell transplantation. The IGF-1 gene was transfected into male SMCs and compared with SMCs transfected with a plasmid vector (vector control) and nontransfected SMCs (cell control). IGF-1 mRNA (n=10/group) and protein levels (n=6/group) were higher (P <0.05 for all groups) at 3, 7, and 14 days compared with controls. VEGF was also increased in parallel to enhanced IGF-1 expression. IGF-1-transfected cells demonstrated greater cell proliferation, stimulated angiogenesis, and decreased caspase-3 activity after simulated ischemia and reperfusion (P <0.05 for all groups compared with vector or cell controls). A uniform left ventricular injury was produced in female rats using a cryoprobe. Three weeks later, 2 x 10(6) cells from three groups were implanted into the scar. One week later, IGF-1-transfected SMCs had increased myocardial IGF-1 and VEGF levels, increased Bcl2 expression, limited cell apoptosis, and enhanced vessel formation in the myocardial scar compared with the two control groups (P <0.05 for all groups). The proportion of SMCs surviving in the implanted region was greater (P <0.05) in the IGF-1-transfected group than in the vector or cell controls. Gene enhancement with IGF-1 improved donor cell proliferation, survival, and engraftment after cell transplantation, perhaps mediated by enhanced angiogenesis and reduced apoptosis. 相似文献
40.
Structure and function of aggrecan 总被引:18,自引:1,他引:17
INTRODUCTIONDegenerative joint disease is a leading sourceof morbidity resulting in significant social and eco-nomic impact. One to 5% of the population underthe age of 45 and 15-85% of oIder individuals sufferfrom some fOrm of degenerative joint disease, mainlyosteoarthritis. Osteoarthritis is characterized by theslow progressive deterioration of articular carti-1age[1, 2]. Current therapeutic regimens addressmainly pain but not degeneration. A better under-standing of the distinct micr… 相似文献