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At least 739 records · Page 41Linked to original sources
PubMed1996

Molecular aspects of design of immunoassays for drugs.

An understanding of the molecular structure of the antibody binding site, the epitope complementary to the antibody, and the intermolecular forces that determine the affinity and specificity of the interaction of antibody and epitope is fundamental to the design of immunoassays. This is particularly important for haptens because their small size results in small changes in substituent functional groups, e.g., optical rotation and carboxyl substitution for amide resulting in large changes in binding affinity. It should be possible to predict the effect of haptenic structure on binding affinity by considering the resulting changes in balance between the different intermolecular forces. This information can be used in designing immunogens and modifying the reaction conditions used during assay optimization, such as pH or ionic strength, that enhance the predominant intermolecular forces to increase the binding affinity but leave minimal matrix effects. Improved understanding of the molecular aspects of the immunological interaction can facilitate more rapid and economic immunoassay development.

Drug Design↗
PubMed2002

Improvements in the understanding and treatment of macular hole.

Recent innovations in macular imaging and surgery have provided important new information concerning the pathogenesis and treatment of idiopathic macular hole. New imaging data suggest that localized perifoveal vitreous detachment (an early stage of age-related posterior vitreous detachment) is the primary pathogenic event in idiopathic macular hole formation. Detachment of the posterior hyaloid from the pericentral retina exerts anterior traction on the foveola and localizes into the foveola the dynamic vitreous traction associated with ocular rotations. Optical coherence tomography has clarified the pathoanatomy of early macular hole stages, beginning with a foveal pseudocyst (stage 1A) and typically followed by disruption of the outer retina (stage 1B) before progressing to a full-thickness dehiscence (stage 2). The treatment of macular hole continues to evolve as modifications to the standard surgical procedure are proposed and evaluated. These innovations include the use of cytokine adjuvants, peeling of the internal limiting membrane, vital staining of the internal limiting membrane with indocyanine green dye, and variations in the length of postoperative face-down positioning.

Diagnostic Techniques, Ophthalmological↗
PubMed2005

The effect of storage time of human red cells on intestinal microcirculatory oxygenation in a rat isovolemic exchange model.

OBJECTIVE: To determine whether the storage time of human leukodepleted red blood cell concentrates compromises intestinal microvascular oxygen concentration oxygen (muPo(2)) during isovolemic exchange transfusion at low hematocrit. DESIGN: Prospective, randomized, controlled study. SETTING: University research institute laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Intestinal muPo(2) was determined by Pd-porphyrin phosphorescence life-time measurements. MEASUREMENTS AND MAIN RESULTS: Rats were brought near to a state of oxygen supply dependency by hemodilution with a pasteurized plasma protein solution to a hematocrit of 14.3 +/- 1.1% (n = 24). Subsequently, an isovolemic exchange transfusion with human leukodepleted red blood cells, stored for 2-6 days (fresh, n = 8), 2-3 wks (intermediate, n = 8), or 5-6 wks (old, n = 8), was performed to determine whether intestinal muPo(2) would be preserved. Immunologic reactions were avoided by washing the red blood cell concentrates three times before use. Isovolemic exchange with fresh and intermediate red blood cells maintained muPo(2) whereas old cells decreased muPo(2) with 26%. Subsequent transfusion with red blood cells (hematocrit approximately 60%) until reaching a hematocrit of 32.4 +/- 2.1 % (n = 24) increased intestinal muPo(2) in all three groups to the same extent between 28% and 32%. No changes in red blood cell deformability, as determined by a Laser-assisted Optical Rotational Cell Analyzer, could be demonstrated during 5 wks of storage. CONCLUSION: This study shows that at low hematocrit, the oxygen-delivering capacity of human red blood cells stored 5-6 wks is reduced compared with fresh cells and red blood cells stored for an intermediate period. Although red blood cells stored for 2-3 wks are completely devoid of 2,3-diphosphoglycerate, their oxygen-delivering capacity to the intestines was the same as fresh red blood cells. Our study showed that red blood cell deformability was preserved during storage, suggesting that other mechanisms may account for the observed decrease in oxygen delivery by red blood cells stored 2-3 wks.

Animals↗
PubMed2003

Hyperaggregating effect of hydroxyethyl starch components and University of Wisconsin solution on human red blood cells: a risk of impaired graft perfusion in organ procurement?

BACKGROUND: The standard preservation solution used during organ procurement and preservation of most organs is the University of Wisconsin (UW) solution. Despite its superiority over other cold storage solutions, the inclusion of hydroxyethyl starch (HES) as one of the components of the UW solution has been both advocated and denied. This study determined whether HES had any effect on red blood cell (RBC) aggregability and correlated aggregation parameters with HES molecular weight. METHODS: Human RBC aggregability and deformability were investigated in vitro, at 4 degrees C, with a laser-assisted optical rotation cell analyzer. The study of RBC aggregation in a binary HES-HES system gave an indication about the nature of HES-RBCs interactions. Bright field microscopy and atomic force microscopy were used to morphologically characterize the aggregates size and form. RESULTS: High molecular weight HES and UW solution had a potent hyperaggregating effect; low molecular weight HES had a hypoaggregating effect on RBC. RBC aggregates were of large size and their resistance to dissociation by flow-induced shear stress was high. CONCLUSION: The authors' in vitro experiments conclusively showed that the physiologic function of RBCs to form aggregates is significantly affected in the presence of HES. The use of high molecular weight HES in UW solution accounts for extended and accelerated aggregation of erythrocytes that may result in stasis of blood and incomplete washout of donor organs before transplantation.

Adenosine↗
PubMed1999

Radiative transfer in chiral random media.

This paper is devoted to the investigation of polarization and radiative characteristics of coherent and diffused light beams in isotropic media with optically active particles. Simple solutions for the Stokes vectors of the direct and diffused beams are obtained in the framework of the vector radiative transfer theory. Results obtained can be used for the generalization of the circular dichroism and optical rotation dispersion spectroscopy for the case of disperse media.

Journal Article↗
PubMed2001

Observation of a reentrant twist grain boundary phase.

We report the occurrence of a reentrant twist grain boundary phase, which we designate as Re- TGB(A). Microscopic observations on a nonsymmetric dimer showed the phase sequence Iso- N*- TGB(A)-Sm- A-Re- TGB(A)- TGB(C*). Here N* and Sm- A stand for the chiral nematic and smectic- A phases, TGB(A) is the twist grain boundary phase with smectic- A blocks, and TGB(C*) that with smectic- C* blocks and exhibiting features of both the smectic- C* and TGB phases. The reentrance of the TGB(A) phase is unambiguously demonstrated using x-ray diffraction, selective reflection, and optical rotation data.

Journal Article↗
PubMed2004

Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry.

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.7 c m(3) at a pressure of 5 bars, natural isotopic abundance, polarization 1% ), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of approximately 10 nG induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio approximately 10 , limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

Journal Article↗
PubMed2004

Can a quantum nondemolition measurement improve the sensitivity of an atomic magnetometer?

We consider the limitations due to noise (e.g., quantum projection noise and photon shot-noise) on the sensitivity of an idealized atomic magnetometer that utilizes spin squeezing induced by a continuous quantum nondemolition measurement. Such a magnetometer measures spin precession of N atomic spins by detecting optical rotation of far-detuned light. We show that for very short measurement times, the optimal sensitivity scales as N(-3/4); if strongly squeezed probe light is used, the Heisenberg limit of N-1 scaling can be achieved. However, if the measurement time exceeds tau(rel)/N(1/2) in the former case, or tau(rel)/N in the latter, where tau(rel) is the spin relaxation time, the scaling becomes N(-1/2), as for a standard shot-noise-limited magnetometer.

Journal Article↗
PubMed2006

Chiral molecules split light: Reflection and refraction in a chiral liquid.

A light beam changes direction as it enters a liquid at an angle from another medium, such as air. Should the liquid contain molecules that lack mirror symmetry, then it has been predicted by Fresnel that the light beam will not only change direction, but will actually split into two separate beams with a small difference in the respective angles of refraction. Here we report the observation of this phenomenon. We also demonstrate that the angle of reflection does not equal the angle of incidence in a chiral medium. Unlike conventional optical rotation, which depends on the path-length through the sample, the reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.

Journal Article↗
PubMed1972

A Phytotoxic Glycopeptide from Cultures of Corynebacterium insidiosum.

Cultures of Corynebacterium insidiosum produce an extra-cellular phytotoxic glycopeptide that possesses the ability to wilt plant cuttings. Wilt induced by this glycopeptide is directly dependent upon time and upon concentration with measureable wilt occurring in 40 nm solutions in 1 hour. The organism produces 1.3 grams toxin/liter of culture medium. The toxin was purified, and the physical, chemical, and biological properties were measured. The glycopeptide has an empirical formula of C(108)H(226)O(132)N based on 1 atom of nitrogen. The molecular weight as estimated by light scattering and column gel chromatography indicated values approximating 5 x 10(6). The toxin does not dissociate into small molecular weight subunits when treated with 8 m urea or 30% pyridine.The toxin has a specific optical rotation of [alpha](5460 A) (34.5 C) = -166 degrees , an intrinsic viscosity of 0.2307 dl/g, and decomposes at 260 C. It has a blue chromophore due to copper chelation at a concentration of 75 moles copper/mole toxin. Mannose, glucose, galactose and l-fucose, with trace amounts of rhamnose and an unidentified reducing sugar, comprise 83.1% of the toxin. An unknown organic acid appearing chemically similar to a keto-deoxy organic acid comprises 8.8% of the toxin. Lysine(2), arginine(1), aspartic acid(1), threonine(1), serine(1), glutamic acid(1), glycine(2), alanine(2), valine(2), leucine(2), and isoleucine(1), form a single peptide with glycine as the sole NH(2)-terminal amino acid. The peptide-carbohydrate linkage appears to be of a glycosidic nature involving the -OH of threonine. This single peptide composes 2.6% of the toxin, and there are 77 moles peptide/mole of purified glycopeptide.

Journal Article↗
PubMed1988

Identification of l-Tryptophan as an Endogenous Inhibitor of Embryo Germination in White Wheat.

An endogenous germination inhibitor(s) in wheat (Triticum aestivum L.) grain has been implicated in seed dormancy and germination, but its identity and mode of action have not been elucidated. We isolated and identified an endogenous germination inhibitor in white wheat grain and compared its activity with that of known compounds. A water extract of wheat bran chromatographed on Sephadex LH-20 yielded an inhibitory fraction that was detected by bioassay on embryos excised from dormant wheat seeds. The inhibitor was sequentially purified by DEAE-cellulose, P-2 gel filtration, and C(18) reversed-phase HPLC and identified as l-tryptophan by carbon and proton nuclear magnetic resonance spectroscopy, mass spectrometry, optical rotation, UV absorption spectrum, and chromatographic co-elution with authentic tryptophan. Extractable tryptophan occurred in wheat grain and bran at about 1.3 to 1.5 and 2.7 to 5.9 milligrams per gram, respectively. Low millimolar concentrations of l-tryptophan similar to physiological levels and d-tryptophan were more inhibitory to embryos from dormant seeds than to embryos from nondormant seeds. Tryptophol and tryptamine, putative intermediates between tryptophan and IAA, were highly inhibitory and noninhibitory of embryo germination, respectively. IAA and 2,4-D also inhibited germination, but embryos from dormant and nondormant seeds responded similarly. l-Tryptophan may be an important germination inhibitor of excised embryos, but its role in situ remains to be determined.

Journal Article↗
PubMed1978

Effect of succinylation on the oligomeric structure of arachin.

Arachin succinylated to various levels has been studied by the techniques of sedimentation velocity, viscosity, absorption and fluorescence spectra, optical rotation and circular dichroism. Succinylation up to 60% leads to the dissociation of the parent 14S molecule to 9S and 4S fractions; above 60% succinylation, 4S fraction occurs predominantly. The other measured properties also show a gradual change up to 50% succinylation and a marked change above this level. The observed changes suggest that a new organised structure is formed before the 4S fraction is denatured.

Arachis↗
PubMed1983

Carbonyldiimidazole/1-hydroxybenzotriazole activation in polymer phase synthesis of the arginine rich proalbumin hexapeptide extension.

The synthesis on different polymer phases of Arg-Gly-Val-Phe-Arg-Arg, the proalbumin extension, is reported. The peptide was prepared both on a 0.5% cross-linked polystyrene gel containing 2-oxoethyl bromide anchor functions and on a 1% cross-linked chloromethyl polystyrene. For temporary blocking of the amino groups we utilized the 2-(3,5-dimethoxyphenyl) propyl-(2)-oxycarbonyl (Ddz). The guanidino groups of the three arginine moieties were protected by the 4-toluenesulfonyl (Tos) group. As coupling procedure we used 1 equiv. carbonyldiimidazole (CDI)/2 equiv. 1-hydroxybenzotriazole (HOBt). The C-terminal activation of the Ddz-amino acids with CDI/HOBt made it possible to recover the excess Ddz-amino acids in 60-80% yield. We also investigated different procedures to cleave the 2-oxoethyl ester bond between the peptide and the polymer. This bond was completely stable against trifluoromethanesulfonic acid and was split by 1 N triethylamine in methanol/dioxane 1:1 (v/v) + 1 vol% 1 N NaOH. The optical rotation and HPLC properties of Arg-Gly-Val-Phe-Arg-Arg from this synthesis are identical to the product from a different synthesis published earlier.

Albumins↗
PubMed1986

Conformation and structure of mildly heat-treated ovalbumin in dilute solutions and gel formation at higher protein concentrations.

The conformation of heat-denatured ovalbumin aggregates has been examined at several concentrations and pH values, using measurements of optical rotation dispersion (ORD), circular dichroism (CD) and viscosity. The protein was subjected to heating at relatively low temperatures, ranging from 48.5 to 76 degrees; the particular temperature chosen depended on pH. The heat treatment was sufficient to remove the ability of the molecules to absorb heat on re-heating. The denatured molecules were shown to be rather compact, i.e. not much larger than the native molecule, and to retain a significant amount of secondary structure; this was also the case for molecules present in small aggregates. It is suggested that this type of ovalbumin monomer builds three-dimensional networks in denatured solutions at higher concentrations, and that gelation should be looked upon as arising from surface contacts between hydrated globules. The present results also imply that such globules have gelation properties which depend on whether pH is acidic or basic compared to the isoelectric point of the protein.

Animals↗
PubMed1990

Synthesis of O-glycosylated tuftsins by utilizing threonine derivatives containing an unprotected monosaccharide moiety.

Synthesis is described of four tuftsin derivatives containing a D-glucopyranosyl or a D-galactopyranosyl unit covalently linked to the hydroxy side chain function of the threonine residue through either an alpha or beta O-glycosidic linkage. Fmoc-threonine derivatives containing the suitable unprotected sugar were used for incorporating the O-glycosylated amino acid residue. Z-Thr[alpha-Glc(OBzl)4]-OBzl and Z-Thr[alpha-Gal(OBzl)4]-OBzl were prepared from the tetra-O-benzylated sugar and Z-Thr-OBzl by the trichloroacetimidate method in the presence of trimethylsilyl trifluoromethane sulfonate. The alpha glycosylated threonine derivatives were converted into Fmoc-Thr(alpha-Glc)-OH and Fmoc-Thr(alpha-Gal)-OH by catalytic hydrogenation followed by acylation with Fmoc-OSu. beta-Glucosylation and beta-galactosylation of threonine were carried out by reacting the proper per-O-acetylated sugar with Z-Thr-OBzl and boron trifluoride ethyl etherate in dichloromethane. Catalytic hydrogenation of the beta-O-glycosylated threonine derivatives followed by acylation with Fmoc-OSu and deacetylation with methanolic hydrazine yielded Fmoc-Thr(beta-Glc)-OH and Fmoc-Thr(beta-Gal)-OH, respectively. The O-glycosylated threonine derivatives were then reacted with H-Lys(Z)-Pro-Arg(NO2)-OBzl in the presence of DCC and HOBt and the resulting glycosylated tuftsin derivatives were fully deblocked by catalytic hydrogenation, purified by HPLC, and characterized by optical rotation, amino acid analysis, and 1H NMR. The beta-galactosylated tuftsin was also prepared by the continuous flow solid phase procedure.

Amino Acid Sequence↗
PubMed1991

Synthesis of glycosylated tuftsins and tuftsin-containing IgG fragment undecapeptide.

Syntheses are described of two new tuftsin derivatives containing a 2-acetamido-2-deoxy-D-galactopyranosyl unit alpha- or beta-glycosidically linked to the threonine's hydroxy side chain function and of the glycosylated undecapeptide corresponding to the tuftsin region of the heavy chain of IgG (amino acid sequence 289-299). The glycosylated tuftsins were synthesized by the solution procedure. Fmoc-[Gal NAc(Ac)3 alpha]Thr-OH and Fmoc-[GalNAc(Ac)3 beta]Thr-OH were allowed to react with H-Lys(Z)-Pro-Arg(NO2)-OBzl by the mixed anhydride procedure and the resulting glycosylated tetrapeptides were fully deblocked by catalytic hydrogenation followed by treatment with potassium cyanide, purified by ion exchange chromatography and characterized by analytical HPLC, elemental and amino acid analyses, optical rotation, and proton NMR spectroscopy. Synthesis of the glycosylated undecapeptide was achieved by the continuous flow solid phase procedure on 4-hydroxymethylphenoxyacetyl-norleucyl derivatized Kieselguhr-supported resin. Fmoc-amino acid symmetrical anhydrides or pentafluorophenyl esters, in the presence of N-hydroxybenzotriazole, were used as the acylating agents. To mimic the native sequence of the tuftsin region at the Fc-domain of immunoglobulin G a 2-acetamido-2-deoxy-beta-D-glucopyranosyl unit was N-glycosidically linked to the amide side chain of Asn 297. The glycosylated asparagine residue was introduced as N2-fluorenylmethyloxycarbonyl-N4-(2-acetamido-3,4,6-tri-O-acetyl-2 -deoxy-beta-D - glucopyranosyl)-asparagine pentafluorophenyl ester. After cleavage from the resin the glycopeptide was deprotected, purified by ion exchange chromatography, and characterized by analytical HPLC, amino acid analysis, high voltage electrophoresis, and proton NMR. The conformational features of the glyco-undecapeptide were determined by circular dichroism measurements both in water and in 98% trifluoroethanol. Results of biological assays will be published elsewhere.

Acylation↗
PubMed1992

Synthesis and biological activity of the mono- and di-galactosyl-vespulakinin 1 analogues.

Syntheses are described of some mono- and di-glycosylated analogues of vespulakinin 1. The solid phase procedure, based on the Fmoc chemistry, was used to prepare (Gal alpha)Thr3-vespulakinin 1, (Gal beta)Thr3-vespulakinin 1 and the di-glycosylated analogue ((Gal alpha)Thr3, (Gal alpha)Thr4-vespulakinin 1. The beta-glycosylated derivative was also prepared by the continuous flow variant of the Fmoc polyamide method. The synthesized glycopeptides were purified and characterized by amino acid analysis, optical rotation, analytical HPLC, 1H- and 13C-NMR and FAB-MS. Preliminary pharmacological experiments showed that the carbohydrate-free vespulakinin 1 is less active than bradykinin (about 0.3 times on a molar basis) when tested by guinea pig rectum contraction, and the two monoglycosylated analogues are equiactive (about 0.9 times the bradykinin activity). The most active derivative, the (Gal alpha)Thr3, (Gal alpha)Thr4-vespulakinin 1 analogue, was about 2.5 times as active as bradykinin.

Acetylation↗