Biomedical subjects

B Bhushan

Publications and source records attributed to B Bhushan.

At least 19 recordsLinked to original sources

PubMed2006

Alkylphosphonate modified aluminum oxide surfaces.

The surface properties of aluminum, such as chemical composition, roughness, friction, adhesion, and wear, can play an important role in the performance of micro-/nano-electromechanical systems, e.g., digital micromirror devices. Aluminum substrates chemically reacted with octadecylphosphonic acid (ODP/Al), decylphosphonic acid (DP/Al), and octylphosphonic acid (OP/Al) have been investigated and characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM). XPS analysis confirmed the presence of alkylphosphonate molecules on ODP/Al, DP/Al, and OP/Al. No phosphonates were found on bare Al as a control. The sessile drop static contact angle of pure water on ODP/Al and DP/Al was typically more than 115 degrees and on OP/Al typically less than 105 degrees indicating that all phosphonic acid reacted Al samples were highly hydrophobic. The root-mean-square surface roughness for ODP/Al, DP/Al, OP/Al, and bare Al was less than 15 nm as determined by AFM. The surface energy for ODP/Al and DP/Al was determined to be approximately 21 and 22 mJ/m2, respectively, by the Zisman plot method, compared to 25 mJ/m2 for OP/Al. ODP/Al and OP/Al were studied by friction force microscopy, a derivative of AFM, to better understand their micro-/nano-tribological properties. ODP/Al gave the lowest coefficient of friction values while bare Al gave the highest. The adhesion forces for ODP/Al and OP/Al were comparable.

Journal Article↗

PubMed2006

Phosphonate self-assembled monolayers on aluminum surfaces.

Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDPAlSi), decylphosphonic acid (DPAlSi), and octadecylphosphonic acid (ODPAlSi) were studied by x-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), and friction force microscopy, a derivative of AFM, to characterize their surface chemical composition, roughness, and micro-/nanotribological properties. XPS analysis confirmed the presence of perfluorinated and nonperfluorinated alkylphosphonate molecules on the PFDPAlSi, DPAlSi, and ODPAlSi. The sessile drop static contact angle of pure water on PFDPAlSi was typically more than 130 degrees and on DPAlSi and ODPAlSi typically more than 125 degrees indicating that all phosphonic acid reacted AlSi samples were very hydrophobic. The surface roughness for PFDPAlSi, DPAlSi, ODPAlSi, and bare AlSi was approximately 35 nm as determined by AFM. The surface energy for PFDPAlSi was determined to be approximately 11 mNm by the Zisman plot method compared to 21 and 20 mNm for DPAlSi and ODPAlSi, respectively. Tribology involves the measure of lateral forces due to friction and adhesion between two surfaces. Friction, adhesion, and wear play important roles in the performance of micro-/nanoelectromechanical systems. PFDPAlSi gave the lowest adhesion and coefficient of friction values while bare AlSi gave the highest. The adhesion and coefficient of friction values for DPAlSi and ODPAlSi were comparable.

Journal Article↗

PubMed2006

Effect of iron(III), humic acids and anthraquinone-2,6-disulfonate on biodegradation of cyclic nitramines by Clostridium sp. EDB2.

AIMS: To determine the biodegradation of cyclic nitramines by an anaerobic marine bacterium, Clostridium sp. EDB2, in the presence of Fe(III), humic acids (HA) and anthraquinone-2,6-disulfonate (AQDS). METHODS AND RESULTS: An obligate anaerobic bacterium, Clostridium sp. EDB2, degraded RDX and HMX, and produced similar product distribution including nitrite, methylenedinitramine, nitrous oxide, ammonium, formaldehyde, formic acid and carbon dioxide. Carbon (C) and nitrogen (N) mass balance for RDX products were 87% and 82%, respectively, and for HMX were 88% and 74%, respectively. Bacterial growth and biodegradation of RDX and HMX were stimulated in the presence of Fe(III), HA and AQDS suggesting that strain EDB2 utilized Fe(III), HA and AQDS as redox mediators to transfer electrons to cyclic nitramines. CONCLUSIONS: Strain EDB2 demonstrated a multidimensional approach to degrade RDX and HMX: first, direct degradation of the chemicals; second, indirect degradation by reducing Fe(III) to produce reactive-Fe(II); third, indirect degradation by reducing HA and AQDS which act as electron shuttles to transfer electrons to the cyclic nitramines. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study could be helpful in determining the fate of cyclic nitramine energetic chemicals in the environments rich in Fe(III) and HA.

Anthraquinones↗

PubMed2006

Atomic force microscopy studies of conditioner thickness distribution and binding interactions on the hair surface.

The way in which common hair care products, such as conditioner, deposit onto and change hair properties is of interest in beauty care science, as these properties are closely tied to product performance. The binding interaction between conditioner and the hair surface is one of the important factors in determining the conditioner thickness distribution and consequently the proper functions of conditioner. In this study, atomic force microscopy was used to obtain the local conditioner thickness distribution, adhesive forces and effective Young's modulus mapping of various hair surfaces. The conditioner thickness was extracted by measuring the forces on the atomic force microscopy tip as it approached, contacted and pushed through the conditioner layer. The effective Young's moduli of various hair surfaces were calculated from the force distance curves using Hertz analysis. The intrinsic binding interactions between different silicones and the hair surface on the microscopic scale, as well as their effect on the effective Young's modulus of the hair, are also discussed. It was found that the effective Young's modulus of the hair is strongly affected by the binding of conditioner molecules on the hair surface.

Hair↗

PubMed2005

Correlations between adhesion hysteresis and friction at molecular scales.

Correlations between adhesion hysteresis and local friction are theoretically and experimentally investigated. The model is based on the classical theory of adhesional friction, contact mechanics, capillary hysteresis, and nanoscale roughness. Adhesion hysteresis was found to scale with friction through the scaling factor containing a varying ratio of adhesion energy over the reduced Young's modulus. Capillary forces can offset the relationship between adhesion hysteresis and friction. Measurements on a wide range of engineering samples with varying adhesive and elastic properties confirm the model. Adhesion hysteresis is investigated under controlled, low humidity atmosphere via ultrasonic force microscopy. Friction is measured by the friction force microscopy.

Journal Article↗

PubMed2005

A theoretical model for the margination of particles within blood vessels.

The margination of a particle circulating in the blood stream has been analyzed. The contribution of buoyancy, hemodynamic forces, van der Waals, electrostatic and steric interactions between the circulating particle and the endothelium lining the vasculature has been considered. For practical applications, the contribution of buoyancy, hemodynamic forces and van der Waals interactions should be only taken into account, whilst the effect of electrostatic and steric repulsion becomes important only at very short distances from the endothelium (1-10 nm). The margination speed and the time for margination t(s) have been estimated as a function of the density of the particle relative to blood delta rho, the Hamaker constant A and radius R of the particle. A critical radius Rc exists for which the margination time t(s) has a maximum, which is influenced by both delta rho and A: the critical radius decreases as the relative density increases and the Hamaker constant decreases. Therefore, particles used for drug delivery should have a radius smaller than the critical value (in the range of 100 nm) to facilitate margination and interaction with the endothelium. While particles used as nanoharvesting agents in proteomics or genomics analysis should have a radius close to the critical value to minimize margination and increase their circulation time.

Blood Flow Velocity↗

PubMed2005

Morphological, nanomechanical and cellular structural characterization of human hair and conditioner distribution using torsional resonance mode with an atomic force microscope.

Characterization of the cellular structure and chemical and physical properties of hair are essential to develop better cosmetic products and advance the biological and cosmetic sciences. Although the morphology of the fine cellular structure of human hair has traditionally been investigated using scanning electron microscopy and transmission electron microscopy, atomic force microscopy can be used for characterization in ambient conditions without requiring specific sample preparations and surface treatment. In this study, the tapping and torsional resonance modes in an atomic force microscope are compared for measurements of stiffness and viscoelastic properties. The materials were mapped using amplitude and phase angle imaging. The torsional resonance mode showed advantages in resolving the in-plane (lateral) heterogeneity of materials. This mode was used for investigating and characterizing the fine cellular structure of human hair. Various cellular structures (such as the cortex and the cuticle) of human hair and fine sublamellar structures of the cuticle, such as the A-layer, the exocuticle, the endocuticle and the cell membrane complex were easily identified. The distribution and thickness of conditioner on the treated hair surface affects the tribological properties of hair. The thickness of the conditioner was estimated using force distance measurements with an atomic force microscope.

Hair↗

PubMed2001

Functional analysis of chimeric proteins of the Wilson Cu(I)-ATPase (ATP7B) and ZntA, a Pb(II)/Zn(II)/Cd(II)-ATPase from Escherichia coli.

ATP7B, the Wilson disease-associated Cu(I)-transporter, and ZntA from Escherichia coli are soft metal P1-type ATPases with mutually exclusive metal ion substrates. P1-type ATPases have a distinctive amino-terminal domain containing the conserved metal-binding motif GXXCXXC. ZntA has one copy of this motif while ATP7B has six copies. The effect of interchanging the amino-terminal domains of ATP7B and ZntA was investigated. Chimeric proteins were constructed in which either the entire amino-terminal domain of ATP7B or only its sixth metal-binding motif replaced the amino-terminal domain of ZntA. Both chimeras conferred resistance to lead, zinc, and cadmium salts but not to copper salts. The purified chimeras displayed activity with lead, cadmium, zinc, and mercury, which are substrates of ZntA. There was no activity with copper or silver, which are substrates of ATP7B. The chimeras were 2-3-fold less active than ZntA. Thus, the amino-terminal domain of P1-type ATPases cannot alter the metal specificity determined by the transmembrane segment. Also, these results suggest that this domain interacts with the rest of the transporter in a metal ion-specific manner; the amino-terminal domain of ATP7B cannot replace that of ZntA in restoring full catalytic activity.

Adenosine Triphosphatases↗

PubMed2001

Efficiency of naphthalene and salicylate degradation by a recombinant Pseudomonas putida mutant strain defective in glucose metabolism.

Metabolically engineered microorganisms may have tremendous potential in removing toxic compounds from nature. In general, microorganisms prefer to utilize simpler carbon sources over toxic compounds when both are present in an environment and, therefore, the presence of simpler carbon sources may greatly reduce the efficiency of a microorganism towards toxic compounds. If a microorganism is prevented from utilizing simpler carbon sources, thereby making it totally dependent upon the toxic compounds, it should increase the specificity for and efficiency of degradation of the toxic compounds in the presence of other, simpler carbon sources. To test this hypothesis, the efficiency of naphthalene and salicylate degradation in the presence of glucose by a recombinant Pseudomonas putida strain mutated in glucose metabolism was determined and compared to the non-mutated strain. Results obtained indicate that the impairment of glucose metabolism leads to better degradation of naphthalene and salicylate in the presence of glucose.

Biodegradation, Environmental↗

PubMed2001

Scavenging of reactive oxygen species by chlorophyllin: an ESR study.

The antioxidant effects of chlorophyllin (CHL), a water-soluble analog of the green plant pigment chlorophyll, on different reactive oxygen species (ROS) were investigated by electron spin resonance (ESR) spectroscopy. As a standard, we have used the ability of CHL to scavenge the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. CHL inhibits the formation of 5,5-dimethyl-1-pyrroline-N-oxide adduct with hydroxyl radical (DMPO-.OH adduct) generated by gamma-radiation in a dose-dependent manner. At a concentration of 1 mM, CHL caused more than 90% inhibition of ESR signal intensity of this adduct. However, the results obtained with the Fenton reaction were different. We also found evidence for the inhibition of 1O2-dependent formation of the 2,2,6,6-tetramethyl-piperidine oxide (TEMPO) radical during photosensitization of methylene blue with visible light. CHL was also able to inhibit hydrogen peroxide induced oxidation of phenol red. The rate constant of the reaction of CHL with H2O2 was found to be 2.7 x 10(6) M-1 s-1. In conclusion, CHL has potent antioxidant ability involving scavenging of various physiologically important ROS.

Bepridil↗

PubMed2001

Cultural variation in hemifacial asymmetry of emotion expressions.

Photographs of hemifacial composites (left-left, right-right and normal presentation, right-left) of these cultures (Japanese, Oriental Indian and North American) displaying six emotions (happy, sad, fear, anger, surprise, disgust) and a neutral state were administered successively (one by one) as well as simultaneously (three hemifacial photographs of an expression at a time) to observers for judgment on a 5-point scale in terms of distinctiveness of expression. Observers' judgments were treated with a culture of expressor x sex of expressor x facial presentation x emotion category mixed factorial ANOVA. Cultures did not vary for their distinctiveness of facial expressions, suggesting universality in this respect. Culture-specificity was, however, observed with respect to hemifacial asymmetry and valence of emotion expressions: (1) Japanese showed a right hemifacial bias for positive and left hemifacial bias for negative emotions; Indians and North Americans showed left hemifacial bias for all emotions, and (2) negative emotion expressions were least distinctly identifiable in Japanese faces followed by Indian and North American faces.

Adolescent↗

PubMed2000

Enhanced production of a thermostable xylanase from Streptomyces sp. QG-11-3 and its application in biobleaching of eucalyptus kraft pulp.

A thermostable and cellulase-free xylanase has been produced from Streptomyces sp. QG-11-3 in solid substrate fermentation using wheat bran and eucalyptus kraft pulp as the prime solid substrates. The maximum xylanase yield obtained using these two substrates were 2360 U/g and 1200 U/g dry solid substrate at substrate:moisture ratios of 1:3 and 1:2.5, respectively. In immobilized cell system using polyurethane foam (PUF) and three nonwoven fabrics, namely, polyester, silk, and cotton, the xylanase yields were enhanced by 2.5-fold (203 U/ml), 1.91-fold (155 U/ml), 1.54-fold (125 U/ml), and 1.47-fold (119 U/ml), respectively, compared to the xylanase yield in liquid-batch fermentation (81 U/ml). In the biobleaching experiments, the xylanase dose of 3.5 U/g moisture free pulp exhibited the optimum bleach boosting of eucalyptus kraft pulp at pH 8.5 and 50 degrees C after 2 h of treatment. When xylanase treated pulp was subsequently treated with 4.5% chlorine, it resulted in reduction of kappa number by 25%, enhanced the brightness (%ISO) by 20% and improved the pulp properties such as tensile strength and burst factor by up to 63% and 8%, respectively.

Journal Article↗

PubMed2000

Chemotaxis and biodegradation of 3-methyl- 4-nitrophenol by Ralstonia sp. SJ98.

3-Methyl-4-nitrophenol is one of the major breakdown products of fenitrothion [O,O-dimethyl O-(3-methyl-4-nitrophenyl) thiophosphate], a recalcitrant organophosphate insecticide used in agriculture. Being the non-polar methylated aromatic compound, 3-methyl-4-nitrophenol is highly toxic and, therefore, a complete degradation of this compound is important for environmental decontamination/bioremediation purposes. A gram negative, motile Ralstonia sp. SJ98 was isolated by selective screening from a soil sample contaminated with pesticides. The microorganism was capable of utilizing 3-methyl-4-nitrophenol as the sole source of carbon and energy. Thin layer chromatography (TLC), gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), and high performance liquid chromatography (HPLC) were performed to determine the possible intermediates in the degradative pathway of this compound. Taken together, catechol was found to be one of the major intermediate of the pathway. Furthermore, the chemotactic behavior of Ralstonia sp. SJ98 towards 3-methyl-4-nitrophenol was tested using three different methods i.e., drop assay, swarm plate assay and capillary assay, which were found to be positive towards this compound. This is the first report clearly indicating the involvement of a microorganism in the chemotaxis and biodegradation of methyl-4-nitrophenol and formation of catechol as an intermediate in the degradative pathway.

Amiloride↗

PubMed2000

Kinetics of biodegradation of p-nitrophenol by different bacteria.

Three bacterial species, i.e., Ralstonia sp. SJ98, Arthrobacter protophormiae RKJ100, and Burkholderia cepacia RKJ200, have been examined for their efficiency and kinetics behavior toward PNP degradation. All the three bacteria utilized PNP as the sole source of carbon, nitrogen, and energy. The rates of radiolabeled [U-(14)C]PNP degradation by all the bacteria were higher in the nitrogen-free medium compared to the medium with nitrogen. The apparent K(m) values of PNP degradation by SJ98, RKJ100, and RKJ200 were 0.32, 0.28, and 0.23 mM, respectively, as determined from the Michaelis-Menten curves. The maximum rates of PNP degradation (V(max)) according to Lineweaver-Burk's plots were 11.76, 7.81, and 3.84 micromol PNP degraded/min/mg dry biomass, respectively. The interpretation drawn from the Lineweaver-Burk's plots showed that the PNP degradation by SJ98 was stimulated by 4-nitrocatechol and 1, 2,4-benzenetriol. Benzoquinone and hydroquinone inhibited PNP degradation by RKJ100 noncompetitively and competitively, respectively, whereas in the case of RKJ200, benzoquinone and hydroquinone inhibited PNP degradation in an uncompetitive manner. beta-Ketoadipate did not affect the rate of PNP degradation in any case.

Arthrobacter↗

PubMed2000

Chemotaxis of a Ralstonia sp. SJ98 toward different nitroaromatic compounds and their degradation.

A Ralstonia sp. SJ98, isolated by a chemotactic enrichment technique, was capable of utilizing different nitroaromatic compounds (NACs). It utilized p-nitrophenol, 4-nitrocatechol, o-nitrobenzoic acid, and p-nitrobenzoic acid as the sole source of carbon and energy. It was observed that Ralstonia sp. SJ98 was chemotactic to the above-mentioned NACs as tested by the drop assay, swarm plate assay, and capillary assay. However, it failed to show chemotactic behavior toward those compounds which were not degraded by the microorganism. This is the first report which shows the chemotaxis of a microorganism toward different NACs and their subsequent degradation. Some of the intermediates of the NACs' degradative pathways have been identified using TLC, GC, and GC-MS studies. The results presented here indicate a correlation between chemotaxis and biodegradation of NACs.

Betaproteobacteria↗

PubMed2000

Isolation, purification and characterization of xylanasefrom Staphylococcus sp. SG-13 and its application in biobleaching of kraft pulp.

A haloalkalophilic Staphylococcus sp. SG-13 produced an alkalistable xylanase in wheat bran medium. A 12-fold purification was achieved by using standard purification techniques. The purified xylanase exhibited a dual pH optima of 7.5 and 9.2. The optimum temperature for enzyme activity was 50 degrees C. The enzyme was stable at 50 degrees C for more than 4 h. The xylanase exhibited Km and Vmax values of 4 mg ml-1, 90 micromol min-1 per mg for birchwood xylan and 7 mg ml-1, 55 micromol min-1 per mg for oatspelt xylan, respectively. The substrate binding affinity of xylanase was more for oatspelt xylan but birchwood xylan was hydrolysed more rapidly. The xylanase activity was stimulated by Fe2+, Ni2+, Cu2+ and dithiothreitol up to 60% and was strongly inhibited in the presence of Co2+, Hg2+, Pb2+, phenyl methane sulphonyl fluoride, ethylenediaminetetraacetic acid, and acetic anhydride up to 100%. The xylanase dose of 1.8 U g-1 moisture free pulp, exhibited bleach boosting of kraft pulps optimally at pH 9.5-10.0 and 50 degrees C after 4 h of reaction time. Pretreatment of pulp with xylanase and its subsequent treatment with 8% hypochlorite, reduced the kappa number by 30%, enhanced the brightness and viscosity by 11% and 1.8%, respectively, and improved the paper properties such as tensile strength and burst factor up to 10% and 17%, respectively.

Chlorine Compounds↗

PubMed2000

Production and characterization of a thermostable chitinase from a new alkalophilic Bacillus sp. BG-11.

An alkalophilic, environmental micro-organism, Bacillus sp. BG-11, has been isolated and characterized. It produced 76 U ml-1 of chitinase in liquid batch fermentation after 72 h of incubation at 50 degrees C using chitin-enriched medium. The molecular weight of purified chitinase was estimated to be 41 kDa by SDS-PAGE. The pH and temperature optima of chitinase immobilized on chitosan and calcium alginate were 8.5 and 50 degrees C, respectively, which were same as that of free enzyme. The pH and thermostability of immobilized chitinase were enhanced significantly. The chitinase immobilized on chitosan was stable between pH 5.0 and 10.0, and the half-life of chitosan-immobilized enzyme at 70, 80 and 90 degrees C was 90, 70 and 60 min, respectively. The end-products formed during the enzyme-substrate reaction were identified by 13C-NMR, and N-acetyl-D-glucosamine was found to be the major end-product. GlcNAc (GlcNAc)2 and (GlcNAc)3 inhibited the chitinase activity by 32, 25 and 18%, respectively, at a concentration of 10 mmol l-1. The shelf-life of chitinase (retained 100% activity) at 4 degrees C was 8 weeks in the presence of either sodium azide (100 microgram ml-1), sodium metabisulphite (0.1% w/v) or KCl (15% w/v). The enzyme was resistant to the action of proteases and allosamidin.

Acetylglucosamine↗

PubMed2000

Indigo production by naphthalene-degrading bacteria.

A wild-type naphthalene-degrading strain Pseudomonas putida RKJ1 and two recombinant strains each of Ps. putida and Escherichia coli carrying the genes for naphthalene degradation on a recombinant plasmid pRKJ3, produced indigo and indirubin pigments from indole. Naphthalene, salicylate and IPTG induced cells of naphthalene-degrading recombinant bacteria produced up to two times higher indigo compared with the uninduced cells. The maximum rates of indigo formation by Ps. putida RKJ1, Ps. putida RKJ5/pRKJ3, Ps. putida KT2442/pRKJ3, E. coli TB1/pRKJ3 and E. coli AB1157/pRKJ3 were 0.60, 0.80, 0.60, 1.20 and 1.50 nmol min-1 mg dry biomass-1, respectively, using indole as the substrate. The apparent Km values of indigo formation by these same bacteria were 0.22, 0.15, 0.10, 0. 21 and 0.20 mmol l-1, respectively, again using indole as the substrate. The present study revealed that E. coli AB1157 was the most efficient of the hosts tested for the expression of the plasmid encoded genes (pRKJ3) from the wild-type strain Ps. putida RKJ1. In addition, both recombinant E. coli strains were capable of producing indigo directly from nutrient medium.

Coloring Agents↗