Farid Khan - Academia.edu (original) (raw)
Papers by Farid Khan
Journal of the Indian Chemical Society, 2008
Imbalance of signals that control cell survival and death results in pathologies, including cance... more Imbalance of signals that control cell survival and death results in pathologies, including cancer and neurodegeneration. Two pathways that are integral to setting the balance between cell survival and cell death are controlled by lipid-activated protein kinase B (PKB)/Akt and Ca 2؉ . PKB elicits its effects through the phosphorylation and inactivation of proapoptotic factors. Ca 2؉ stimulates many prodeath pathways, among which is mitochondrial permeability transition. We identified Ca 2؉ release through inositol 1,4,5-trisphosphate receptor (InsP3R) intracellular channels as a prosurvival target of PKB. We demonstrated that in response to survival signals, PKB interacts with and phosphorylates InsP3Rs, significantly reducing their Ca 2؉ release activity. Moreover, phosphorylation of InsP3Rs by PKB reduced cellular sensitivity to apoptotic stimuli through a mechanism that involved diminished Ca 2؉ flux from the endoplasmic reticulum to the mitochondria. In glioblastoma cells that exhibit hyperactive PKB, the same prosurvival effect of PKB on InsP3R was found to be responsible for the insensitivity of these cells to apoptotic stimuli. We propose that PKB-mediated abolition of InsP3-induced Ca 2؉ release may afford tumor cells a survival advantage.
Background: SDI tracks influenza by collecting clinical, demographic, vaccine status, medical his... more Background: SDI tracks influenza by collecting clinical, demographic, vaccine status, medical history and rapid testing data from ~20,000 patients with influenza-like illness (ILI) seen in ~400 primary physician offices across the US each season. Furthermore, SDI tracks patterns in vaccine dose administration in physician's offices using a large national sample of medical claims. Objectives: To generate near-real time influenza vaccine coverage estimates Methods: We estimated influenza vaccination coverage from the primary surveillance system in the subset of ILI patients seen during November 1 through December 10 2009, and who tested negative for influenza virus. Medical claims data from CMS-1500 forms featuring procedure codes for pandemic and seasonal doses were used to generate temporal uptake patterns and total doses administered in physician's offices. Results: We included 1607 rapid-test negative ILI patients in the study; of these, 431 had received seasonal vaccine, ...
MRS Proceedings, 2000
ABSTRACT We have measured high spatial/depth resolution (2-3 µm) thermal conductivity (κ) at 300K... more ABSTRACT We have measured high spatial/depth resolution (2-3 µm) thermal conductivity (κ) at 300K before and after plasma-induced effects on a series of n-GaN/sapphire (0001) samples fabricated by hydride vapor phase epitaxy (HVPE) using a ThermoMicroscope's ...
BMC Bioinformatics, 2010
Background: The behaviour of biological systems can be deduced from their mathematical models. Ho... more Background: The behaviour of biological systems can be deduced from their mathematical models. However, multiple sources of data in diverse forms are required in the construction of a model in order to define its components and their biochemical reactions, and corresponding parameters. Automating the assembly and use of systems biology models is dependent upon data integration processes involving the interoperation of data and analytical resources. Results: Taverna workflows have been developed for the automated assembly of quantitative parameterised metabolic networks in the Systems Biology Markup Language (SBML). A SBML model is built in a systematic fashion by the workflows which starts with the construction of a qualitative network using data from a MIRIAMcompliant genome-scale model of yeast metabolism. This is followed by parameterisation of the SBML model with experimental data from two repositories, the SABIO-RK enzyme kinetics database and a database of quantitative experimental results. The models are then calibrated and simulated in workflows that call out to COPASIWS, the web service interface to the COPASI software application for analysing biochemical networks. These systems biology workflows were evaluated for their ability to construct a parameterised model of yeast glycolysis.
Soft Matter, 2009
Hierarchically structured polysaccharide sponges have been prepared by freeze drying of anisotrop... more Hierarchically structured polysaccharide sponges have been prepared by freeze drying of anisotropically ordered alginatedextran hydrogels produced by dissipative densification in the presence of a uniaxial Ca 2+ ion diffusion gradient. The freeze-dried gels exhibit elastic/viscoelastic ...
Expert review of anti-infective therapy, 2015
Urinary tract infections (UTIs) represent an important cause of febrile illness in young children... more Urinary tract infections (UTIs) represent an important cause of febrile illness in young children and can lead to renal scarring and kidney failure. However, diagnosis and treatment of recurrent UTI in children is an area of some controversy. Guidelines from the American Academy of Pediatrics, National Institute for Health and Clinical Excellence and European Society of Paediatric Radiology differ from each other in terms of the diagnostic algorithm to be followed. Treatment of vesicoureteral reflux and antibiotic prophylaxis for prevention of recurrent UTI are also areas of considerable debate. In this review, we collate and appraise recently published literature in order to formulate evidence-based guidance for the diagnosis and treatment of recurrent UTI in children.
International Journal of Materials Science and Engineering, 2013
ABSTRACT An electrodynamic harvester for scavenging acoustic energy is reported in this paper. Th... more ABSTRACT An electrodynamic harvester for scavenging acoustic energy is reported in this paper. The working principle, fabrication and characterization of the harvester are discussed. The developed harvester consists of an Helmholtz resonator, flexible membrane, moving magnets and a fixed wound coil. The harvester is characterized under acoustic energy at different sound pressure levels (SPL’s) and is subjected to both increasing frequency sweep (IFS) and decreasing frequency sweep (DFS). At resonance and under 120 dB SPL, the harvester produced a maximum load rms voltage of 315 mV at 66 Ω load resistance. The experimental results showed the maximum power delivered to load is 1503.4 μW at 120 dB SPL, that leads to a maximum power density of 191.4 μW/cm3 for the developed harvester. The energy harvester is also characterized in open air with a large speaker as an acoustic source. Moreover, the harvester generated a load voltage of about 30 mV when subjected to the acoustical noise of a household electrical generator.
Protein Engineering Design and Selection, 2008
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 2001
Four cases-of congenital dysfunction of the major salivary glands as well as of Prader-Willi, con... more Four cases-of congenital dysfunction of the major salivary glands as well as of Prader-Willi, congenital rubella, and Sjögren's syndromes-were identified in a series of 500 patients referred for excessive tooth wear. Although there was evidence of consumption of highly acidic drinks, some occlusal parafunction, and unacceptable toothbrushing habits, salivary dysfunction was the salient factor predisposing a patient to tooth wear in these syndromal cases. The 500 subjects have been characterized either as having medical conditions and medications that predispose them to xerostomia or lifestyles in which workplace- and sports-related dehydration lead to reduced salivary flow. Normal salivation, by buffering capacity, clearance by swallowing, pellicle formation, and capacity for remineralization of demineralized enamel, protects the teeth from extrinsic and intrinsic acids that initiate dental erosion. Thus, the syndromes, unrelated in many respects, underline the importance of normal salivation in the protection of teeth against tooth wear by erosion, attrition, and abrasion.
Nucleic Acids Research, 2009
Mapping the landscape of possible macromolecular polymer sequences to their fitness in performing... more Mapping the landscape of possible macromolecular polymer sequences to their fitness in performing biological functions is a challenge across the biosciences. A paradigm is the case of aptamers, nucleic acids that can be selected to bind particular target molecules. We have characterized the sequence-fitness landscape for aptamers binding allophycocyanin (APC) protein via a novel Closed Loop Aptameric Directed Evolution (CLADE) approach. In contrast to the conventional SELEX methodology, selection and mutation of aptamer sequences was carried out in silico, with explicit fitness assays for 44 131 aptamers of known sequence using DNA microarrays in vitro. We capture the landscape using a predictive machine learning model linking sequence features and function and validate this model using 5500 entirely separate test sequences, which give a very high observed versus predicted correlation of 0.87. This approach reveals a complex sequence-fitness mapping, and hypotheses for the physical basis of aptameric binding; it also enables rapid design of novel aptamers with desired binding properties. We demonstrate an extension to the approach by incorporating prior knowledge into CLADE, resulting in some of the tightest binding sequences.
Nature Methods, 2008
We describe a method, DNA array to protein array (DAPA), which allows the 'printing' of replicate... more We describe a method, DNA array to protein array (DAPA), which allows the 'printing' of replicate protein arrays directly from a DNA array template using cell-free protein synthesis. At least 20 copies of a protein array can be obtained from a single DNA array. DAPA eliminates the need for separate protein expression, purification and spotting, and also overcomes the problem of long-term functional storage of surface-bound proteins.
Materials Science and Engineering: C, 2010
Polysaccharides such as sodium alginate, sodium carboxymethylcellulose (CMC) and dextran readily ... more Polysaccharides such as sodium alginate, sodium carboxymethylcellulose (CMC) and dextran readily form hydrogels with diverse properties and applications. For example polysaccharide gels are useful as binders, stabilizers, emulsifiers, film-forming agents, suspending ...
Malaria Journal, 2013
Background: Drug repurposing or repositioning refers to the usage of existing drugs in diseases o... more Background: Drug repurposing or repositioning refers to the usage of existing drugs in diseases other than those it was originally used for. For diseases like malaria, where there is an urgent need for active drug candidates, the strategy offers a route to significantly shorten the traditional drug development pipelines. Preliminary highthroughput screens on patent expired drug libraries have recently been carried out for Plasmodium falciparum. This study reports the systematic and objective further interrogation of selected compounds reported in these studies, to enable their repositioning as novel stand-alone anti-malarials or as combinatorial partners. Methods: SYBR Green flow cytometry and micro-titre plate assays optimized in the laboratory were used to monitor drug susceptibility of in vitro cultures of P. falciparum K1 parasite strains. Previously described fixed-ratio methods were adopted to investigate drug interactions. Results: Emetine dihydrochloride hydrate, an anti-protozoal drug previously used for intestinal and tissue amoebiasis was shown to have potent inhibitory properties (IC 50 doses of~47nM) in the multidrug resistant K1 strain of P. falciparum. The sum 50% fractional inhibitory concentration (∑FIC 50, 90 ) of the interaction of emetine dihydrochloride hydrate and dihydroartemisinin against the K1 strains of P. falciparum ranged from 0.88-1.48. Conclusion: The results warrant further investigation of emetine dihydrochloride hydrate as a potential stand-alone anti-malarial option. The interaction between the drug and the current front line dihydroartemisinin ranged from additive to mildly antagonistic in the fixed drug ratios tested.
Journal of the Chilean Chemical Society, 2013
Journal of the American Chemical Society, 2006
Biosynthetic preparation and 19 F NMR experiments on uniformly 3-fluorotyrosine-labeled green flu... more Biosynthetic preparation and 19 F NMR experiments on uniformly 3-fluorotyrosine-labeled green fluorescent protein (GFP) are described. The 19 F NMR signals of all 10 fluorotyrosines are resolved in the protein spectrum with signals spread over 10 ppm. Each tyrosine in GFP was mutated in turn to phenylalanine. The spectra of the Tyr f Phe mutants, in conjunction with relaxation data and results from 19 F photo-CIDNP (chemically induced dynamic nuclear polarization) experiments, yielded a full 19 F NMR assignment. Two 19 F-Tyr residues (Y92 and Y143) were found to yield pairs of signals originating from ring-flip conformers; these two residues must therefore be immobilized in the native structure and have 19 F nuclei in two magnetically distinct positions depending on the orientation of the aromatic ring. Photo-CIDNP experiments were undertaken to probe further the structure of the native and denatured states. The observed NMR signal enhancements were found to be consistent with calculations of the HOMO (highest occupied molecular orbital) accessibilities of the tyrosine residues. The photo-CIDNP spectrum of native GFP shows four peaks corresponding to the four tyrosine residues that have solvent-exposed HOMOs. In contrast, the photo-CIDNP spectra of various denatured states of GFP show only two peaks corresponding to the 19 Flabeled tyrosine side chains and the 19 F-labeled Y66 of the chromophore. These data suggest that the pH-denatured and GdnDCl-denatured states are similar in terms of the chemical environments of the tyrosine residues. Further analysis of the sign and amplitude of the photo-CIDNP effect, however, provided strong evidence that the denatured state at pH 2.9 has significantly different properties and appears to be heterogeneous, containing subensembles with significantly different rotational correlation times. method (geometry/NMR) |2σzz − (σxx + σyy)| /ppm |σxx − σyy| /ppm DFT B3LYP 6-311++G(2d,2p)/ CSGT DFT B3LYP cc-pVDZ 238 44 DFT B3LYP 6-311++G(2d,2p)/ GIAO DFT B3LYP 6-311++G(2d,2p) 271 54 DFT B3LYP 6-311++G(2d,2p)/ GIAO HF 6-311++G(2d,2p) 210 44 A R T I C L E S Khan et al. D J. AM. CHEM. SOC.
Journal of Orthopaedic Surgery and Research, 2011
This study will seek to identify a measurable radiographic index, the Metaphyseal-Diaphyseal Inde... more This study will seek to identify a measurable radiographic index, the Metaphyseal-Diaphyseal Index (MDI) score to determine whether intra-operative fracture in osteoporotic bone can be predicted.
Journal of Biomolecular NMR, 2000
Journal of Applied Physics, 2002
We have measured high spatial/depth resolution (23 μm) thermal conductivity (κ) at 300 K before ... more We have measured high spatial/depth resolution (23 μm) thermal conductivity (κ) at 300 K before and after plasma-induced effects on two series of n-GaN sapphire (0001) samples fabricated by hydride vapor phase epitaxy using scanning thermal microscopy. The sample ...
Journal of the Indian Chemical Society, 2008
Imbalance of signals that control cell survival and death results in pathologies, including cance... more Imbalance of signals that control cell survival and death results in pathologies, including cancer and neurodegeneration. Two pathways that are integral to setting the balance between cell survival and cell death are controlled by lipid-activated protein kinase B (PKB)/Akt and Ca 2؉ . PKB elicits its effects through the phosphorylation and inactivation of proapoptotic factors. Ca 2؉ stimulates many prodeath pathways, among which is mitochondrial permeability transition. We identified Ca 2؉ release through inositol 1,4,5-trisphosphate receptor (InsP3R) intracellular channels as a prosurvival target of PKB. We demonstrated that in response to survival signals, PKB interacts with and phosphorylates InsP3Rs, significantly reducing their Ca 2؉ release activity. Moreover, phosphorylation of InsP3Rs by PKB reduced cellular sensitivity to apoptotic stimuli through a mechanism that involved diminished Ca 2؉ flux from the endoplasmic reticulum to the mitochondria. In glioblastoma cells that exhibit hyperactive PKB, the same prosurvival effect of PKB on InsP3R was found to be responsible for the insensitivity of these cells to apoptotic stimuli. We propose that PKB-mediated abolition of InsP3-induced Ca 2؉ release may afford tumor cells a survival advantage.
Background: SDI tracks influenza by collecting clinical, demographic, vaccine status, medical his... more Background: SDI tracks influenza by collecting clinical, demographic, vaccine status, medical history and rapid testing data from ~20,000 patients with influenza-like illness (ILI) seen in ~400 primary physician offices across the US each season. Furthermore, SDI tracks patterns in vaccine dose administration in physician's offices using a large national sample of medical claims. Objectives: To generate near-real time influenza vaccine coverage estimates Methods: We estimated influenza vaccination coverage from the primary surveillance system in the subset of ILI patients seen during November 1 through December 10 2009, and who tested negative for influenza virus. Medical claims data from CMS-1500 forms featuring procedure codes for pandemic and seasonal doses were used to generate temporal uptake patterns and total doses administered in physician's offices. Results: We included 1607 rapid-test negative ILI patients in the study; of these, 431 had received seasonal vaccine, ...
MRS Proceedings, 2000
ABSTRACT We have measured high spatial/depth resolution (2-3 µm) thermal conductivity (κ) at 300K... more ABSTRACT We have measured high spatial/depth resolution (2-3 µm) thermal conductivity (κ) at 300K before and after plasma-induced effects on a series of n-GaN/sapphire (0001) samples fabricated by hydride vapor phase epitaxy (HVPE) using a ThermoMicroscope's ...
BMC Bioinformatics, 2010
Background: The behaviour of biological systems can be deduced from their mathematical models. Ho... more Background: The behaviour of biological systems can be deduced from their mathematical models. However, multiple sources of data in diverse forms are required in the construction of a model in order to define its components and their biochemical reactions, and corresponding parameters. Automating the assembly and use of systems biology models is dependent upon data integration processes involving the interoperation of data and analytical resources. Results: Taverna workflows have been developed for the automated assembly of quantitative parameterised metabolic networks in the Systems Biology Markup Language (SBML). A SBML model is built in a systematic fashion by the workflows which starts with the construction of a qualitative network using data from a MIRIAMcompliant genome-scale model of yeast metabolism. This is followed by parameterisation of the SBML model with experimental data from two repositories, the SABIO-RK enzyme kinetics database and a database of quantitative experimental results. The models are then calibrated and simulated in workflows that call out to COPASIWS, the web service interface to the COPASI software application for analysing biochemical networks. These systems biology workflows were evaluated for their ability to construct a parameterised model of yeast glycolysis.
Soft Matter, 2009
Hierarchically structured polysaccharide sponges have been prepared by freeze drying of anisotrop... more Hierarchically structured polysaccharide sponges have been prepared by freeze drying of anisotropically ordered alginatedextran hydrogels produced by dissipative densification in the presence of a uniaxial Ca 2+ ion diffusion gradient. The freeze-dried gels exhibit elastic/viscoelastic ...
Expert review of anti-infective therapy, 2015
Urinary tract infections (UTIs) represent an important cause of febrile illness in young children... more Urinary tract infections (UTIs) represent an important cause of febrile illness in young children and can lead to renal scarring and kidney failure. However, diagnosis and treatment of recurrent UTI in children is an area of some controversy. Guidelines from the American Academy of Pediatrics, National Institute for Health and Clinical Excellence and European Society of Paediatric Radiology differ from each other in terms of the diagnostic algorithm to be followed. Treatment of vesicoureteral reflux and antibiotic prophylaxis for prevention of recurrent UTI are also areas of considerable debate. In this review, we collate and appraise recently published literature in order to formulate evidence-based guidance for the diagnosis and treatment of recurrent UTI in children.
International Journal of Materials Science and Engineering, 2013
ABSTRACT An electrodynamic harvester for scavenging acoustic energy is reported in this paper. Th... more ABSTRACT An electrodynamic harvester for scavenging acoustic energy is reported in this paper. The working principle, fabrication and characterization of the harvester are discussed. The developed harvester consists of an Helmholtz resonator, flexible membrane, moving magnets and a fixed wound coil. The harvester is characterized under acoustic energy at different sound pressure levels (SPL’s) and is subjected to both increasing frequency sweep (IFS) and decreasing frequency sweep (DFS). At resonance and under 120 dB SPL, the harvester produced a maximum load rms voltage of 315 mV at 66 Ω load resistance. The experimental results showed the maximum power delivered to load is 1503.4 μW at 120 dB SPL, that leads to a maximum power density of 191.4 μW/cm3 for the developed harvester. The energy harvester is also characterized in open air with a large speaker as an acoustic source. Moreover, the harvester generated a load voltage of about 30 mV when subjected to the acoustical noise of a household electrical generator.
Protein Engineering Design and Selection, 2008
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 2001
Four cases-of congenital dysfunction of the major salivary glands as well as of Prader-Willi, con... more Four cases-of congenital dysfunction of the major salivary glands as well as of Prader-Willi, congenital rubella, and Sjögren's syndromes-were identified in a series of 500 patients referred for excessive tooth wear. Although there was evidence of consumption of highly acidic drinks, some occlusal parafunction, and unacceptable toothbrushing habits, salivary dysfunction was the salient factor predisposing a patient to tooth wear in these syndromal cases. The 500 subjects have been characterized either as having medical conditions and medications that predispose them to xerostomia or lifestyles in which workplace- and sports-related dehydration lead to reduced salivary flow. Normal salivation, by buffering capacity, clearance by swallowing, pellicle formation, and capacity for remineralization of demineralized enamel, protects the teeth from extrinsic and intrinsic acids that initiate dental erosion. Thus, the syndromes, unrelated in many respects, underline the importance of normal salivation in the protection of teeth against tooth wear by erosion, attrition, and abrasion.
Nucleic Acids Research, 2009
Mapping the landscape of possible macromolecular polymer sequences to their fitness in performing... more Mapping the landscape of possible macromolecular polymer sequences to their fitness in performing biological functions is a challenge across the biosciences. A paradigm is the case of aptamers, nucleic acids that can be selected to bind particular target molecules. We have characterized the sequence-fitness landscape for aptamers binding allophycocyanin (APC) protein via a novel Closed Loop Aptameric Directed Evolution (CLADE) approach. In contrast to the conventional SELEX methodology, selection and mutation of aptamer sequences was carried out in silico, with explicit fitness assays for 44 131 aptamers of known sequence using DNA microarrays in vitro. We capture the landscape using a predictive machine learning model linking sequence features and function and validate this model using 5500 entirely separate test sequences, which give a very high observed versus predicted correlation of 0.87. This approach reveals a complex sequence-fitness mapping, and hypotheses for the physical basis of aptameric binding; it also enables rapid design of novel aptamers with desired binding properties. We demonstrate an extension to the approach by incorporating prior knowledge into CLADE, resulting in some of the tightest binding sequences.
Nature Methods, 2008
We describe a method, DNA array to protein array (DAPA), which allows the 'printing' of replicate... more We describe a method, DNA array to protein array (DAPA), which allows the 'printing' of replicate protein arrays directly from a DNA array template using cell-free protein synthesis. At least 20 copies of a protein array can be obtained from a single DNA array. DAPA eliminates the need for separate protein expression, purification and spotting, and also overcomes the problem of long-term functional storage of surface-bound proteins.
Materials Science and Engineering: C, 2010
Polysaccharides such as sodium alginate, sodium carboxymethylcellulose (CMC) and dextran readily ... more Polysaccharides such as sodium alginate, sodium carboxymethylcellulose (CMC) and dextran readily form hydrogels with diverse properties and applications. For example polysaccharide gels are useful as binders, stabilizers, emulsifiers, film-forming agents, suspending ...
Malaria Journal, 2013
Background: Drug repurposing or repositioning refers to the usage of existing drugs in diseases o... more Background: Drug repurposing or repositioning refers to the usage of existing drugs in diseases other than those it was originally used for. For diseases like malaria, where there is an urgent need for active drug candidates, the strategy offers a route to significantly shorten the traditional drug development pipelines. Preliminary highthroughput screens on patent expired drug libraries have recently been carried out for Plasmodium falciparum. This study reports the systematic and objective further interrogation of selected compounds reported in these studies, to enable their repositioning as novel stand-alone anti-malarials or as combinatorial partners. Methods: SYBR Green flow cytometry and micro-titre plate assays optimized in the laboratory were used to monitor drug susceptibility of in vitro cultures of P. falciparum K1 parasite strains. Previously described fixed-ratio methods were adopted to investigate drug interactions. Results: Emetine dihydrochloride hydrate, an anti-protozoal drug previously used for intestinal and tissue amoebiasis was shown to have potent inhibitory properties (IC 50 doses of~47nM) in the multidrug resistant K1 strain of P. falciparum. The sum 50% fractional inhibitory concentration (∑FIC 50, 90 ) of the interaction of emetine dihydrochloride hydrate and dihydroartemisinin against the K1 strains of P. falciparum ranged from 0.88-1.48. Conclusion: The results warrant further investigation of emetine dihydrochloride hydrate as a potential stand-alone anti-malarial option. The interaction between the drug and the current front line dihydroartemisinin ranged from additive to mildly antagonistic in the fixed drug ratios tested.
Journal of the Chilean Chemical Society, 2013
Journal of the American Chemical Society, 2006
Biosynthetic preparation and 19 F NMR experiments on uniformly 3-fluorotyrosine-labeled green flu... more Biosynthetic preparation and 19 F NMR experiments on uniformly 3-fluorotyrosine-labeled green fluorescent protein (GFP) are described. The 19 F NMR signals of all 10 fluorotyrosines are resolved in the protein spectrum with signals spread over 10 ppm. Each tyrosine in GFP was mutated in turn to phenylalanine. The spectra of the Tyr f Phe mutants, in conjunction with relaxation data and results from 19 F photo-CIDNP (chemically induced dynamic nuclear polarization) experiments, yielded a full 19 F NMR assignment. Two 19 F-Tyr residues (Y92 and Y143) were found to yield pairs of signals originating from ring-flip conformers; these two residues must therefore be immobilized in the native structure and have 19 F nuclei in two magnetically distinct positions depending on the orientation of the aromatic ring. Photo-CIDNP experiments were undertaken to probe further the structure of the native and denatured states. The observed NMR signal enhancements were found to be consistent with calculations of the HOMO (highest occupied molecular orbital) accessibilities of the tyrosine residues. The photo-CIDNP spectrum of native GFP shows four peaks corresponding to the four tyrosine residues that have solvent-exposed HOMOs. In contrast, the photo-CIDNP spectra of various denatured states of GFP show only two peaks corresponding to the 19 Flabeled tyrosine side chains and the 19 F-labeled Y66 of the chromophore. These data suggest that the pH-denatured and GdnDCl-denatured states are similar in terms of the chemical environments of the tyrosine residues. Further analysis of the sign and amplitude of the photo-CIDNP effect, however, provided strong evidence that the denatured state at pH 2.9 has significantly different properties and appears to be heterogeneous, containing subensembles with significantly different rotational correlation times. method (geometry/NMR) |2σzz − (σxx + σyy)| /ppm |σxx − σyy| /ppm DFT B3LYP 6-311++G(2d,2p)/ CSGT DFT B3LYP cc-pVDZ 238 44 DFT B3LYP 6-311++G(2d,2p)/ GIAO DFT B3LYP 6-311++G(2d,2p) 271 54 DFT B3LYP 6-311++G(2d,2p)/ GIAO HF 6-311++G(2d,2p) 210 44 A R T I C L E S Khan et al. D J. AM. CHEM. SOC.
Journal of Orthopaedic Surgery and Research, 2011
This study will seek to identify a measurable radiographic index, the Metaphyseal-Diaphyseal Inde... more This study will seek to identify a measurable radiographic index, the Metaphyseal-Diaphyseal Index (MDI) score to determine whether intra-operative fracture in osteoporotic bone can be predicted.
Journal of Biomolecular NMR, 2000
Journal of Applied Physics, 2002
We have measured high spatial/depth resolution (23 μm) thermal conductivity (κ) at 300 K before ... more We have measured high spatial/depth resolution (23 μm) thermal conductivity (κ) at 300 K before and after plasma-induced effects on two series of n-GaN sapphire (0001) samples fabricated by hydride vapor phase epitaxy using scanning thermal microscopy. The sample ...