Home About us Contact
|
Home About us Contact | ||
|
|
||
M Phosphate Buffer (m + phosphate_buffer)
Selected AbstractsAmperometric Glucose Biosensors Based on Glassy Carbon and SWCNT-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 1 2008Irene Carpani Abstract Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochemical activation at +1.80,V (vs. SCE) for 900,s, have been used with the aim of comparing their performances in the development of enzyme electrodes. Commercial SWCNTs have been pretreated with 2.2,M HNO3 for 20,h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors has been confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solutions of 0.1,M phosphate buffer (pH,5.5), containing dissolved oxygen, at a potential of ,0.40,V vs. SCE. Although the performances of the two carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addition, the preparation procedure of such biosensors was more simple, rapid and reproducible. [source] A thermal study on the use of immobilized penicillin G acylase in the formation of 7-amino-3-deacetoxy cephalosporanic acid from cephalosporin GJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2004Jian-Liang Pan Abstract Penicillin G acylase (PGA) is an important enzyme for the industrial production of 7-amino-3-deacetoxy cephalosporanic acid (7-ADCA) from cephalosporin G (Ceph-G), and 6-aminopenicillanic acid (6-APA) from penicillin G (Pen-G). These products are used for the manufacture of semi-synthetic cephalosporins and penicillins. In this study, immobilized PGA was utilized to catalyze the conversion of Ceph-G to 7-ADCA. The optimal conditions were found to be an operating temperature of 45 °C, 0.2 M phosphate buffer, a substrate concentration of 30 mg cm,3 and a catalyst particle concentration of 0.01 g cm,3 (specific activity of 623.2 U g,1). Up to 45 °C the reaction was characterized by an activation energy of 38.66 kJ mol,1. Beyond 57.5 °C there was a sharp decline of activity, characterized by a deactivation energy of 235.88 kJ mol,1. Copyright © 2004 Society of Chemical Industry [source] Species-Specific Effects of Sarcoplasmic Extracts on Lipid Oxidation in vitroJOURNAL OF FOOD SCIENCE, Issue 1 2009R. Ramanathan ABSTRACT:, The degree to which lipid and myoglobin (Mb) oxidation processes interact in meat can be species-specific. We investigated the effects of beef and pork sarcoplasmic extracts containing different Mb concentrations on lipid oxidation in a liposome system. Sarcoplasm was extracted from beef and pork longissimus dorsi and psoas major muscles. Beef sarcoplasm was diluted with 0.1 M phosphate buffer to obtain a Mb concentration equivalent to that in pork sarcoplasm. Conversely, equine heart Mb was added to pork sarcoplasm to match the myoglobin concentration of beef sarcoplasm. This resulted in beef and pork sarcoplasms, each with 2 different Mb concentrations for the longissimus (0.02 mM and 0.07 mM) and psoas (0.05 and 0.12 mM). Sarcoplasm (or phosphate buffer control) was incorporated within a phosphatidylcholine liposome preparation and incubated at 25°C. Thiobarbituric acid reactive substances (TBARS) were measured at 0, 30, 60, 90, and 120 min of incubation. Regardless of species, greater Mb concentration within the sarcoplasm increased lipid oxidation (P < 0.05). Across muscles, pork sarcoplasm had lower TBARS values than beef sarcoplasm (P < 0.05). Our results suggest that pork sarcoplasm has a lesser effect on lipid oxidation than beef sarcoplasm for a common Mb concentration. However, increased myoglobin concentration within sarcoplasm promotes lipid oxidation regardless of species. [source] Preparation and biodistribution of [125I]Melphalan: a potential radioligand for diagnostic and therapeutic applicationsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2010A. M. Amin Abstract This paper addresses the development of a new radiopharmaceutical for cancer imaging and therapy. The optimization of the labeling conditions of thymidine analogue, melphalan, with125I is described. High radiochemical yield 96.8% was obtained by reacting 0.2,mg melphalan with 125I in the presence of choloramin-T as oxidizing agent in 0.5,M phosphate buffer, pH 7, at 70°C for 15,min. Preliminary in vivo study was done in non-tumor bearing mice. The results revealed that this new tracer,125I-melphalan, has a high affinity to be localized in the tumor site for a long period, which indicates the specificity of this tracer to the tumor cells. The labeled compound was cleared quickly from most of the body organs. These findings suggest that 125I-melphalan allows imaging and treatment of cancer. 125I-melphalan meets most of the requirements necessary to be used as a successful diagnostic and therapeutic agent: it is a low-molecular-weight molecule that diffuses readily in the tissues, and dose not induce an antibody response. Copyright © 2009 John Wiley & Sons, Ltd. [source] A non-peptide radioiodinated high affinity melanocortin-4 receptor ligandJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11 2003Felikss Mutulis Abstract 4-Cyclohexyl-4-[(1,2,4-triazol-1-yl)methyl]piperidine was introduced into stepwise peptide synthesis procedures using Boc chemistry and derivatives of D -4-iodophenylalanine and D -1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid. A halogen replacement analogue (I-Mex2) of a known high affinity melanocortin-4 receptor selective compound resulted. It showed a subnanomolar affinity when evaluated on the melanocortin-4 receptor in competition with the , -MSH peptide analogue 125I-NDP-MSH. By treatment with hexamethylditin and tetrakis(triphenylphosphine) palladium I-Mex2 was converted to the corresponding trimethylstannyl derivative. In the next step, Na125I was oxidized by an iodobead. Iododestannylation proceeded in the presence of 1 M phosphate buffer, pH 2.5, and the radio-active derivative 125I-Mex2 formed was separated by HPLC at 40% radiochemical yield. Preliminary investigation showed that 125I-Mex2 is useful as a radioligand for melanocortin-4 receptor binding studies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Chromatographic methods for the separation of biocompatible iron chelators from their synthetic precursors and iron chelatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004Petra Kova, íková Abstract Chromatographic methods have been developed for the separation of the three novel biocompatible iron chelators pyridoxal isonicotinoyl hydrazone (PIH), salicylaldehyde isonicotinoyl hydrazone (SIH), and pyridoxal 2-chlorobenzoyl hydrazone (o-108) from their synthetic precursors and iron chelates. The chromatographic analyses were achieved using analytical columns packed with 5 ,m Nucleosil 120-5 C18. For the evaluation of all chelators in the presence of the synthetic precursors, EDTA was added to the mobile phase at a concentration of 2 mM. The best separation of PIH and its synthetic precursors was achieved using a mixture of phosphate buffer (0.01 M NaH2PO4, 5 mM 1-heptanesulfonic acid sodium salt; pH 3.0) and methanol (55 : 45, v/v). For separation of SIH and its synthetic precursors, the mobile phase was composed of 0.01 M phosphate buffer (pH 6.0) and methanol (60 : 40, v/v). o-108 was analyzed employing a mixture of 0.01 M phosphate buffer (pH 7.0), methanol, and acetonitrile (60 : 20 : 20, v/v/v). These mobile phases were slightly modified to separate each chelator from its iron chelate. Furthermore, a RP-TLC method has also been developed for fast separation of all compounds. The chromatographic methods described herein could be applied in the evaluation of purity and stability of these drug candidates. [source] Effect of UV irradiation on type I collagen fibril formation in neutral collagen solutionsPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 3 2001Julian M. Menter Background: Collagens have the well-known ability to spontaneously self-associate to form fibrils at physiological temperature and neutral pH in vitro and in vivo. Because solar UV may photochemically alter collagen, the kinetics of fibril formation may be modified. Thus, we have begun a systematic study of the effect of various UV wavebands on fibril formation. Methods: Citrate-soluble calf skin collagen (Elastin Products) was dissolved at 0.05% in 0.5 M HOAc, dialyzed over 2 days into two changes of 0.0327 M phosphate buffer, pH 7.0 at 4 °C, and centrifuged at 48 000×g. Photolysis was carried out at 4 °C with either (a) UVC (UVG,11 lamp), (b) filtered solar-simulating radiation (SSR) or UVA (SSR or UVL,21 lamp filtered with a 2.0 mm Schott WG 345 filter). Gelation was commenced by rapidly raising the temperature from 8 °C to 33 °C. Nucleation and growth were followed by turbidimetric measurements at 400 nm. Results: UVC radiation (0,17.3 J/cm2) resulted in a dose-dependent decrease in the rate of fibril growth. Under these conditions, concomitant collagen cross-linking and degradation occurred. Fibril nucleation, a prerequisite for growth, was rapid (threshold , 2 min) and was not affected by UVC, UVA or SSR. SSR (0,1320 J/cm2) caused a small decrease in growth rate and in the degree of fibril formation. UVA radiation (0,1080 J/cm2) had a similar effect. "Direct" photochemical damage thus paralleled absorption via various collagen chromophores, with UVC>SSR,UVA. The presence of riboflavin (RF) resulted in ground-state interactions that markedly altered both nucleation and growth kinetics. Irradiation with 29.6 J/cm2 UVA in the presence of RF photosensitizer caused relatively minor additional changes in fibrillation kinetics. Conclusions: These results collectively indicate that fibril formation is markedly dependent on specific ground state interactions and relatively insensitive to nonspecific UV damage. On the other hand, fibrils thus formed from photochemically altered collagen may have altered structural properties that could have subtle but unfavorable effects on the local dermal milieu in vivo. Notwithstanding, the relative insensitivity of fibrillogenesis to non-specific photochemical damage probably represents a favorable adaptation, overall, which tends to conserve the mechanical integrity of the skin. [source] Melatonin is as Effective as Testosterone in the Prevention of Soleus Muscle Atrophy Induced by Castration in RatsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2008Jale Öner Abstract The purpose of this experiment was to compare the weight, insulin-like growth factor-I (IGF-I) expression, and ultrastructure of the soleus muscle in growing castrated rats treated with testosterone or melatonin. In this study, adult male Wistar albino rats were used. The groups were arranged as sham, castrated, and testosterone- or melatonin-injected groups after castration. The soleus muscle samples were fixed in Bouin's solution for immunohistochemistry, and in 2.5% gluteraldehyde in 0.1 M phosphate buffer (pH 7.4). Whereas castration reduced the soleus weight and fiber diameter, testosterone and melatonin administration increased them. IGF-I immunostaining observed in the satellite cells and periphery of the myofibers was least intense in the castrated group. Strong staining of IGF-I was observed in the testosterone- and melatonin-administered groups. The ultrastructure of the soleus muscle in castrated animals showed the important ultrastructural modifications related to degeneration. In these groups, degenerative mitochondria, glycogen clusters under the sarcolemma, irregular Z lines, and loss of lamina externa were observed. The ultrastructure of myofibrils in the testosterone- and melatonin-injected groups was similar to that in sham groups in view of structure. In conclusion, we suggest that melatonin is as effective as testosterone in the prevention of atrophy induced by castration through the IGF-I axis. Anat Rec, 291:448,455, 2008. © 2008 Wiley-Liss, Inc. [source] A sensitive and specific HPGPC-FD method for the study of pharmacokinetics and tissue distribution of Radix Ophiopogonis polysaccharide in ratsBIOMEDICAL CHROMATOGRAPHY, Issue 8 2010Xiao Lin Abstract Interest in antimyocardial ischemic activity of a graminan-type fructan with a weight average molecular weight of 4.8,kDa extracted from Radix Ophiopogonis (ROP) has necessitated the study of its pharmacokinetics and tissue distribution. For that, a simple HPGPC,FD method was developed for the sensitive and specific determination of FITC-ROP (fluorescein,isothiocyanate-labeled ROP) in plasma and rat tissues (heart, liver, spleen, lung, kidney, brain and stomach). The analyte was separated on a Shodex Sugar KS-802 high-performance gel column with 0.1,M phosphate buffer (pH 7.0) as mobile phase at a flow rate of 0.5,mL/min, and fluorescence detection at ,ex 495,nm and ,em 515,nm. The calibration curve for FITC-ROP was linear over the range 0.25,20.0 or 50.0,,g/mL in all studied biosamples with correlation coefficients >0.995. The inter-day and intra-day precisions of analysis were not more than 10%, and assay accuracy ranged from 93 to 105% for plasma and from 89 to 108% for tissue homogenates. This method has been confirmed here to be suitable for the study of pharmacokinetics and tissue distribution of ROP and the achieved results are highly instructive for the further pharmaceutical development of ROP, suggesting the promising application of the method to the increasingly important carbohydrate-based drugs. Copyright © 2009 John Wiley & Sons, Ltd. [source] Cyclic resolution of racemic ibuprofen via coupled efficient lipase and acid-base catalysisCHIRALITY, Issue 3 2009Ying Liu Abstract Extracellular lipase LIP prepared in our lab from the yeast Yarrowia lipolytica was used for the resolution of racemic ibuprofen. The (S)-enantiomer was preferred by lipase LIP, and the unreacted (R)-enantiomer was extracted and racemized in basic solvent-water medium to be re-resolved. Solvent, content of solvent, base concentration, and temperature have a strong effect on racemization. The (S)-ester was separated and hydrolyzed to (S)-ibuprofen in acidic dimethyl sulfoxide-water mixture containing 70% dimethyl sulfoxide. The high purity (S)-ibuprofen (ee = 0.98) was obtained using lipase LIP to catalyze hydrolysis of (S)-ester in 0.1 M phosphate buffer (pH = 8). Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] Optical techniques to determine thermal effects on proteinsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 11 2008Teepakorn Kongraksawech Summary Optical rotation (OR) and transmitted light (TL) measurements were conducted on 1%, 2.5% and 5% (w/v) bovine serum albumin (BSA) in 0.01 m phosphate buffer at pH 7 and ionic strength 0.08. Denaturation temperatures (Td) obtained from OR measurements were consistent with reported differential scanning calorimetry values. Protein concentration did not affect Td in agreement with most reports. Changes in TL reflecting gel formation and protein aggregation were influenced by BSA concentration. Sugar concentration in the range used in this study (0,5%) did not affect the thermal stability of BSA. The lack of difference in sucrose, trehalose and sorbitol effects on the thermal stability of BSA was consistent with some but not all reports. The optical system used to study protein denaturation had acceptable accuracy (consistency with published Td values) and precision (coefficient of variation under 3.5%) levels. [source] Investigation of solute permeation across hydrogels composed of poly(methyl vinyl ether- co -maleic acid) and poly(ethylene glycol)JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2010Thakur Raghu Raj Singh Abstract Objectives, Swelling kinetics and solute permeation (theophylline, vitamin B12 and fluorescein sodium) of hydrogels composed of poly(methyl vinyl ether- co -maleic acid) (PMVE/MA) and poly(ethylene glycol) (PEG) are presented. Methods, The effects of PMVE/MA and PEG 10 000 content on swelling behaviour (percentage swelling, the type of diffusion and swelling rate constant) were investigated in 0.1 m phosphate buffer. Network parameters, such as average molecular weight between crosslinks (Mc) and crosslink density, were evaluated. Key findings, The percentage swelling and Mc of hydrogels increased with decrease in PMVE/MA content, where the water diffusion mechanism into the hydrogels was Class-II type. In contrast, increase in PMVE/MA content caused an increase in the crosslink density. Permeation of theophylline, vitamin B12 and fluorescein sodium, with increasing hydrodynamic radii, was studied through the equilibrium swollen hydrogels composed of PMVE/MA and PEG. In general, the permeability and diffusion coefficients of all three solutes decreased with increase in the PMVE/MA content. In addition, permeability and diffusion coefficient values increased with decreases in the hydrodynamic radii of the solute molecules. Conclusions, The hydrogels have shown a change in swelling behaviour, crosslink density, Mc and solute permeation with change in PMVE/MA content, thus suggesting a potential application in controlled drug-delivery systems. [source] Application of poly(acrylic acid) superporous hydrogel microparticles as a super-disintegrant in fast-disintegrating tabletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2004Shicheng Yang ABSTRACT Poly(acrylic acid) superporous hydrogel (SPH) microparticles possessing a unique porous structure were used as a wicking agent to decrease disintegration time of fast-disintegrating tablets (FDTs). The compression behaviour of poly(acrylic acid) SPH microparticles was evaluated using the Kawakita equation. Effects of various SPH microparticle sizes and a 19-run fractional factorial design were evaluated. The factorial design was based on four factors consisting of ketoprofen, SPH microparticle, filler, and tableting pressure, and each factor contained three levels on the disintegration time and tensile strength of the prepared FDTs. The poly(acrylic acid) SPH microparticles existed in an amorphous state and swelled approximately 80-times in distilled water and 50-times in pH 6.8 0.2 m phosphate buffer. The compressibility of SPH microparticles increased significantly as the microparticle size increased. The FDTs made of SPH microparticles in the range of 75,106 ,m showed the fastest disintegration time and higher tensile strength. SPH microparticle, tableting pressure and ketoprofen had significant effects on disintegration time and tensile strength of ketoprofen FDTs. The FDTs that were prepared with 2.5% w/w SPH microparticles of 75,106 ,m at 63 MPa pressure possessed a tensile strength of 84.4+4.1 N cm,2 and disintegrated in 15.0+2.0 s. It was concluded that the poly(acrylic acid) SPH microparticles could serve as a good super-disintegrant decreasing the disintegration time of FDTs. [source] | |||||||||||||