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91.
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93.
Subrata Mondal 《Computer methods in biomechanics and biomedical engineering》2013,16(16):1247-1257
AbstractOne of the major causes of implant loosening is due to excessive bone resorption surrounding the implant due to bone remodelling. The objective of the study is to investigate the effects of implant material and implant–bone interface conditions on bone remodelling around tibia bone due to total ankle replacement. Finite element models of intact and implanted ankles were developed using CT scan data sets. Bone remodelling algorithm was used in combination with FE analysis to predict the bone density changes around the ankle joint. Dorsiflexion, neutral, and plantar flexion positions were considered, along with muscle force and ligaments. Implant–bone interfacial conditions were assumed as debonded and bonded to represent non-osseointegration and fully osseointegration at the porous coated surface of the implant. To investigate the effect of implant material, three finite element models having different material combinations of the implant were developed. For model 1, tibial and talar components were made of Co–Cr–Mo, and meniscal bearing was made of UHMWPE. For model 2, tibial and talar components were made of ceramic and meniscal bearing was made of UHMWPE. For model 3, tibial and talar components were made of ceramic and meniscal bearing was made of CFR-PEEK. Changes in implant material showed no significant changes in bone density due to bone remodelling. Therefore, ceramic appears to be a viable alternative to metal and CFR-PEEK can be used in place of UHMWPE. This study also indicates that proper bonding between implant and bone is essential for long-term survival of the prosthetic components. 相似文献
94.
Shovan Mondal Jean‐Valère Naubron Damien Campolo Michel Giorgi Michéle P. Bertrand Malek Nechab 《Chirality》2013,25(12):832-839
The absolute configurations (AC) of azaheterocylic compounds resulting from the cascade rearrangement of enediynes involving only light atoms were unambiguously assigned by the joint use of vibrational circular dichroism (VCD) and copper radiation single crystal X‐ray diffraction (XRD). These AC determinations proved that the rearrangements of enediynes proceeded with memory of chirality and retention of configuration. Chirality 25:832–839, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
95.
Cloning and characterization of thermotolerant xylitol dehydrogenases from yeast Pichia angusta 总被引:1,自引:0,他引:1
Dipanwita Biswas Manish Datt Kaliannan Ganesan Alok K. Mondal 《Applied microbiology and biotechnology》2010,88(6):1311-1320
Pichia angusta (syn. Hansenula polymorpha) represents one of the rare yeast that can grow and ferment both xylose and glucose at higher temperature (50°C). However,
little is known about the enzymes involved in xylose utilization from this species. Previous studies indicated the presence
of one xylose reductase and two xylitol dehydrogenase genes in P. angusta. In this study, we have expressed both xylitol dehydrogenases (PaXdh1p and PaXdh2p) in Escherichia coli and purified them as 6X-Histidine-tagged proteins. Biochemical characterization of the recombinant proteins reveals that
both PaXdh1p and PaXdh2p are thermotolerant enzymes. PaXdh2p contains a catalytic and a structural Zn atom. However, the structural
Zn atom is not present in PaXdh1p. Both enzymes also differ in their affinity for the substrate as well as in the catalytic
efficiency. Through mutagenesis and modeling approaches, we have also identified residues important for catalysis and substrate
binding. 相似文献
96.
Dipanwita Biswas Manish Datt Monika Aggarwal Alok K. Mondal 《Applied microbiology and biotechnology》2013,97(4):1613-1623
Because of its natural ability to utilize both xylose and arabinose, the halotolerant and osmotolerant yeast Debaryomyces hansenii is considered as a potential microbial platform for exploiting lignocellulosic biomass. To gain better understanding of the xylose metabolism in D. hansenii, we have cloned and characterized a xylitol dehydrogenase gene (DhXDH). The cloned gene appeared to be essential for xylose metabolism in D. hansenii as the deletion of this gene abolished the growth of the cells on xylose. The expression of DhXDH was strongly upregulated in the presence of xylose. Recombinant DhXdhp was expressed and purified from Escherichia coli. DhXdhp was highly active against xylitol and sorbitol as substrate. Our results showed that DhXdhp was thermo-sensitive, and except this, its biochemical properties were quite comparable with XDH from other yeast species. Furthermore, to make this enzyme suitable for metabolic engineering of D. hansenii, we have improved its thermotolerance and modified cofactor requirement through modelling and mutagenesis approach. 相似文献
97.
Dibyendu Mondal Eric M. Koehn Jiajun Yao David F. Wiemer Amnon Kohen 《Bioorganic & medicinal chemistry》2018,26(9):2365-2371
Exocyclic olefin variants of thymidylate (dTMP) recently have been proposed as reaction intermediates for the thymidyl biosynthesis enzymes found in many pathogenic organisms, yet synthetic reports on these materials are lacking. Here we report two strategies to prepare the exocyclic olefin isomer of dTMP, which is a putative reaction intermediate in pathogenic thymidylate biosynthesis and a novel nucleotide analog. Our most effective strategy involves preserving the existing glyosidic bond of thymidine and manipulating the base to generate the exocyclic methylene moiety. We also report a successful enzymatic deoxyribosylation of a non-aromatic nucleobase isomer of thymine, which provides an additional strategy to access nucleotide analogs with disrupted ring conjugation or with reduced heterocyclic bases. The strategies reported here are straightforward and extendable towards the synthesis of various pyrimidine nucleotide analogs, which could lead to compounds of value in studies of enzyme reaction mechanisms or serve as templates for rational drug design. 相似文献
98.
Ashim Paul Sourav Kumar Sourav Kalita Anup Kumar Ghosh Amal Chandra Mondal Bhubaneswar Mandal 《International journal of peptide research and therapeutics》2018,24(1):201-211
Aggregation of Amyloid β (Aβ) in the interneuronal spaces is a major etiopathological factor for onset and progression of Alzheimer’s disease (AD). Since the mechanism of aggregation is not fully understood, control and modulation of the aggregation process is a challenging task. Although, several strategies were developed for the past few decades, yet there is no proper therapeutics available. Herein, we report a peptide based pro-drug, termed as a conformational Pro-Drug peptide (PDp), which disrupts existing Aβ fibrils, but does not produce toxic soluble oligomers, through a series of spontaneous chemical reactions resulting in in situ generation of β-sheet destabilizing factors. Furthermore, PDp reduces Aβ mediated toxicity examined on an in vitro model consisting of the human neuroblastoma SH-SY5Y cells. PDp also disrupts fibrils originated from AD affected human cerebrospinal fluid. These findings will help to understand the process of amyloidogenesis better and also indicate a novel approach for therapeutically important peptide design. 相似文献
99.
Singh Hemant Kumar Mondal Som Arunachalam Balraj Soman Anishkumar Sharma Pratibha Solanki C. S. 《Plasmonics (Norwell, Mass.)》2018,13(2):705-714
Plasmonics - In this paper, focus is on the light trapping surface in crystalline silicon (c-Si) solar cells where thinner c-Si wafers are expected to be used by industry to reduce the cost of cell... 相似文献
100.
AbstractWe summarize several computational techniques to determine relative free energies for condensed-phase systems. The focus is on practical considerations which are capable of making direct contact with experiments. Particular applications include the thermodynamic stability of apo- and holo-myoglobin, insulin dimerization free energy, ligand binding in lysozyme, and ligand diffusion in globular proteins. In addition to provide differential free energies between neighboring states, converged umbrella sampling simulations provide insight into migration barriers and ligand dissociation barriers and analysis of the trajectories yield additional insight into the structural dynamics of fundamental processes. Also, such simulations are useful tools to quantify relative stability changes for situations where experiments are difficult. This is illustrated for NO-bound myoglobin. For the dissociation of benzonitrile from lysozyme it is found that long umbrella sampling simulations are required to approximately converge the free energy profile. Then, however, the resulting differential free energy between the bound and unbound state is in good agreement with estimates from molecular mechanics with generalized Born surface area simulations. Furthermore, comparing the barrier height for ligand escape suggests that ligand dissociation contains a non-equilibrium component. 相似文献