Syneresis and its possible role in cataractogenesis.
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Cataract↗
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Derivation of midinfrared (5-25 micrometers) optical constants of some silicates and palagonite.
The midinfrared 2000-400 cm-1 (5-25 micrometers) optical constants (real (n) and imaginary (k) indices of refraction) are presented for: (1) pyrophyllite; (2) kaolinite; (3) serpentine; (4) montmorillonite; (5) saponite; (6) palagonite; and (7) orthopyroxene. Comparison of the values derived here with those previously presented for serpentine, montmorillonite, and palagonite is generally quite good and discrepancies between values are probably due to either chemical differences between the actual samples or different techniques used to derive the values. For montmorillonite, saponite, and palagonite we were able to derive optical constants in the region of the H2O-bending fundamental near 6 micrometers. We find that if a pellet of pure material can be produced with a mirror-like surface then the optical constants of clays and other noncohesive materials can be readily derived.
Aluminum Silicates↗
Stress-distribution in the alveolar bone.
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Alveolar Process↗
Determination of reducing and non-reducing carbohydrates in food products by liquid chromatography with post-column catalytic hydrolysis and derivatization. Comparison with refractive index detection.
Post-column catalytic hydrolysis combined with 4-aminobenzoic acid hydrazide derivatization is employed for the determination of both reducing and non-reducing carbohydrates in a variety of complex sample matrices such as dairy products, processed foods and tobaccos. Comparison with refractive index detection shows the post-column method to be superior from the standpoint of selectivity, sensitivity and simplicity of sample preparation. Limits of detection are in the low-nanogram range. Quantitative results are presented for the determination of sugars in potato extracts. The method is also applicable for the separation and detection of carbohydrate oligomers.
Beverages↗
Biospecific interaction analysis using surface plasmon resonance detection applied to kinetic, binding site and concentration analysis.
A system for real-time biospecific interaction analysis using biosensor technology based on the optical phenomenon surface plasmon resonance is described. The biospecific interface is a sensor chip covered with a hydrogel matrix. One component of the interaction to be studied is immobilized covalently to the hydrogel and other interactants are passed over the chip in solution. The mass change at the sensor surface, reflecting the progress of the interaction studied, is monitored in real time. The technique, which does not require molecular labels for detection, can measure mass changes down to 10 pg/mm2. Repeated analyses can be performed on the same sensor chip. Applications shown include kinetic measurements, binding site analysis and concentration determination.
Antibodies, Monoclonal↗
Interfacing gradient elution ion-exchange chromatography and low-angle laser light-scattering photometry for analysis of proteins.
Molecular weights (MWs) of different proteins were determined by interfacing gradient elution ion-exchange chromatography and low-angle laser light-scattering photometry (IEC-LALLS). A high-performance strong cation-exchange column was used to elute proteins using fast (5 min) and conventional (15-30 min) gradients. The eluted proteins were characterized on-line by determining their MWs using LALLS. The specific refractive index (RI) increment (dn/dc) and the RI of the solvent used over the gradient range were determined off-line and used to calculate the absolute weight-average MWs. Four proteins, ribonuclease A, alpha-chymotrypsinogen A, trypsinogen and beta-lactoglobulin A (beta-LACT) were studied. Accurate MWs were obtained for all the proteins using fast and conventional gradients, except for beta-LACT, which aggregated as a function of the gradient employed. The degree of aggregation of beta-LACT increased as the rapidity of the gradient was increased over a fixed gradient range. This study indicated that it is possible to separate and characterize proteins rapidly using IEC-LALLS.
Chromatography, Ion Exchange↗
Optimization of a peak compression system for a remoxipride metabolite (FLA797) and its application to bioanalysis.
A peak compression system is optimized for FLA797 (I), a phenolic tertiary amine and a metabolite to the antipsychotic drug remoxipride. An application is described where this effect is used to give a 6-7-fold improvement of the quantification limit in an assay of I in plasma. The liquid chromatographic system is constructed so that the injection of I dissolved in a solution of a competing amine gives a very high and narrow analyte peak with an apparent efficiency of 1.5 x 10(6) plates/m. When the levels of I in plasma are determined, an internal standard, giving a normal isocratic peak, is added to the plasma sample before the extraction. Concentrations of I down to 0.5-1.0 nM can be determined with reasonable precision. FLA908, another phenolic remoxipride metabolite and a regioisomer to I, eluting as a normal isocratic peak, can be determined simultaneously although only at concentrations higher than 10-15 nM.
Animals↗
Reversed-phase high-performance liquid chromatography of the cardiac glycoside LNF-209 with refractive index detection.
LNF-209 is a glycoside, similar to digoxin, which has potential for use in the treatment of congestive heart failure. However, unlike digoxin it exhibits virtually no useful UV absorption spectra, making detection difficult. One means of detection is the refractive index detector, but like most bulk property detectors it has certain limitations. Its sensitivity is limited and it is sensitive to small changes in a number of parameters, such as temperature, mobile phase composition, and flow-rate. These parameters must be closely controlled to obtain a stable baseline. This paper describes the steps taken to control the system and the development and validation of an assay for LNF-209 in dosing solutions. The method developed is capable of quantitating LNF-209 in solutions of sterile water and 5% dextrose at concentrations ranging from 8 to 6000 micrograms/ml. The method is linear over this range and quantitative recovery is obtained. The overall average relative standard deviation for replicate analysis of several samples at various concentrations assayed over two days was 2.3%.
Androstanes↗
Characterization of further association of the trimeric membrane protein porin by low-angle laser-light scattering photometry coupled with high-performance gel chromatography.
Porin (OmpF), a trimeric membrane protein, in an extract of the outer membrane of Escherichia coli gave a twin-peaked elution pattern on Sephacryl S-300HR gel chromatography in the presence of sodium dodecyl sulphate. The species eluting earlier and later were found to be the hexamer and trimer, respectively, from molecular mass determination by low-angle laser-light scattering photometry coupled with TSK-G3000SWXL gel chromatography. As the hexamer was dissociated into the trimer under the conditions of sodium dodecyl sulphate polyacrylamide gel electrophoresis, its presence had been overlooked. The addition of lipopolysaccharide, another component of the outer membrane, and subsequent dialysis induced association of the trimer, the product containing an appreciable amount of the hexamer.
Chromatography, Gas↗
Determination of beta-(1-3),(1-4)-D-glucans in barley by reversed-phase high-performance liquid chromatography.
An HPLC method for the determination of beta-glucan in barley was developed. The beta-glucan was hydrolysed with lichenase [endo-beta-(1-3),(1-4)-D-glucan-4-glucanhydrolase from Bacillus subtilis] to oligosaccharides, which were analysed by reversed-phase HPLC using water as the mobile phase at a flow-rate of 0.7 ml/min. The separation of the oligosaccharides was performed in a C18 stainless-steel column (Spherisorb ODS-2) with 5-microns particles in less than 10 min, with a refractive index detection.
Carbohydrate Conformation↗
Kinetic analysis of monoclonal antibody-antigen interactions with a new biosensor based analytical system.
An automated biosensor system for measuring molecular interactions has been used to study the kinetics of monoclonal antibody-antigen reactions. The system combines a microfluidic unit in contact with a sensor surface for surface plasmon resonance detection. The specificity of the surface is determined by the operator. Antibody or antigen is immobilised in a dextran matrix attached to the sensor surface. The interaction of matrix bound antibody or antigen with the corresponding partner in solution is monitored in real time. None of the interacting molecules needs to be labelled and it is not necessary to determine the concentration of the the matrix bound component in advance. Two systems were studied: matrix bound monoclonal antibodies (MAbs) interacting with HIV-1 core protein p24 and immobilised aminotheophylline reacting with MAbs. Control of the amount of immobilised ligand and reusable sensor surfaces permits the comparison of different MAbs reacting with antigen under almost identical conditions. Differences in affinity and reaction rates are immediately apparent. The calculated association rate constants for p24 MAbs ranged from 3 x 10(4) - 7.4 x 10(5) M-1 s-1 and for theophylline MAbs association rate constants as high as 1 x 10(6) M-1 s-1 were encountered. The calculated dissociation rate constants were in the region 2 x 10(-4) s-1 to 2 x 10(-2) s-1.
Antibodies, Monoclonal↗
An ophthalmoscope is not a retinoscope. The difference is in the red reflex.
Both the retinoscope and the ophthalmoscope allow observation of the fundus and of the "red reflex." Retinoscopy, however, requires an effective light source that may be quickly moved off the visual axis. The ophthalmoscope is unable to provide this type of illumination. On the other hand, the retinoscope is unable to provide sufficient illumination of the retina to make it useful for ophthalmoscopy . Ophthalmoscopy requires the examiner's retina to be conjugate to the retina being examined, whereas the examiner's retina becomes conjugate to the peephole of the retinoscope in retinoscopy. The "red reflex" seen with either the retinoscope or the ophthalmoscope may be clear or blurred. The clear red reflex is more useful for ophthalmoscopy , while the blurred red reflex is primarily used for retinoscopy.
Humans↗
The molecular weight of bacteriophage phi 6 and its nucleocapsid.
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Bacteriophages↗
An analytic, gradient index schematic lens and eye for the rat which predicts aberrations for finite pupils.
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Animals↗
Astigmatism of oblique incidence in the human model eye.
Two cylindrical lenses of equal power, one positive and one negative, were used to correct astigmatism of oblique incidence in a wide-angle optical model of the human eye. Tangential and sagittal vergences were calculated at different visual angles from the posterior pole to the peripheral retina. The positive cylinder was placed with its axis parallel to the tangential meridian while the negative cylinder was placed with its axis parallel to the sagittal meridian. Improvement in the quality of the retinal image at different angles of incidence was obtained by varying the angle between the axes of the correcting cylinders. Corresponding gains in resolution have been calculated and confirmed by peripheral fundus photography.
Astigmatism↗
Measurement of refractive index in an intact crystalline lens.
A knowledge of the refractive index distribution within the crystalline lens is necessary to define the optical properties of the eye. This report describes the first nondestructive method for measuring the refractive index of intact crystalline lenses based on the work of Chu (1977) [Electron Lett. 13, 736-738] and Barrell and Pask (1978) [Opt. Commun. 27, 230-234] for optical fibre preforms. The method is simpler and more accurate than previous methods and shows that the rat crystalline lens has a smooth and almost parabolic distribution of refractive index.
Animals↗
The refractive increments of bovine alpha-, beta-, and gamma-crystallins.
The refractive increments have been determined for purified bovine alpha-, beta- and gamma-crystallins, using three different light sources. The values obtained were used to predict the refractive index gradient in the rat lens. Excellent agreement was obtained between the predicted and observed gradients.
Animals↗
Stiles-Crawford effect in garter snake.
The optical geometry of the eye of the American garter snake suggests a highly pronounced Stiles-Crawford effect occurs at the level of its cone photoreceptors. However, it is demonstrated here that inner segments of the cones in this species have a high density of microdroplets, up to 0.1 microns in diameter, which increases the refractive index of the ellipsoid. Theoretical considerations involving geometrical optics show that these droplets, like conventional oil droplets, may be a specific adaptation of the garter snake to increase the sensitivity of its cones to oblique rays, thus reducing the potentially large Stiles-Crawford effect predicted for this vertebrate.
Animals↗