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Results for “Optical Rotation”

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At least 811 records · Page 45Linked to original sources
PubMed2001

Isolation and characterizartion of alginic acid from commercially cultured Nemacystus decipiens (Itomozuku).

An alginate was isolated from commercially cultured Nemacystus decipiens which had been harvested in Yonashiro Town (Okinawa, Japan). The yield of the alginate was 1.6% (w/w of wet alga), and the uronic acid, ash and moisture contents of the alginate were 86.0%, 12.0%, and 2.3% (w/w), respectively. The molecular mass of the alginate was estimated to be about 1.5 x 10(5). The infrared spectrum and optical rotation of the alginate were in agreement with those of the standard alginate. D-Mannuronic acid and L-guluronic acid were identified by 1H- and 13C-NMR spectroscopy, the molar ratio of both sugar residues being estimated to be 0.72:1.00.

Alginates↗
PubMed2003

Efficient synthesis of akolactone A via Pd-catalyzed carbonylation.

The first synthesis of (+)- and (-)-akolactone A is described by using Pd-catalyzed carbonylation. A comparison of the optical rotation of both enantiomers of akolactone A and the natural compound suggests that the absolute configuration at the 4-position of akolactone A is R.

4-Butyrolactone↗
PubMed2002

Photon folding for imaging in nonfocusing telescopes.

We present a new technique--photon folding--for imaging in nonfocusing telescopes. Inspired by the epoch-folding method in timing analysis, the photon-folding technique directly provides the statistical significance of signals in images, by use of projection matrices. The technique is robust against common imaging problems such as aspect errors and a nonuniform background. The technique provides a deterministic recursive algorithm for improving images, which can be implemented on line. The higher-order photon-folding technique allows a systematic correction for coding noises, which is suitable for studying weak sources in the presence of highly variable strong sources. The technique can be applied to various types of nonfocusing telescopes such as coded-aperture optics, rotational collimators, or Fourier grid telescopes.

Journal Article↗
PubMed2004

Experimental synchronization of chaos in diode lasers with polarization-rotated feedback and injection.

We demonstrate experimental chaos synchronization between two chaotic semiconductor lasers subjected to polarization-rotated optical feedback and unidirectional injection. This system allows high-quality synchronization to be obtained between dissimilar lasers in a wide range of chaotic operating regimes. Another feature of this system is its operation at high characteristic frequencies, taking advantage of all-optical implementation. Time series and RF spectra showing synchronization are confirmed by high correlation coefficients in excess of 0.85.

Journal Article↗
PubMed2006

Nonlinear forward scattering in cesium vapor: experiment with simultaneous scanning of laser frequency and B-field.

We present the results of an experimental study of nonlinear magneto-optical rotation in a buffer-gas-free uncoated Cs cell on hyperfine transitions F(g) = 3 --> F(e) = 2, 3, 4 of the D(2) line at high laser irradiance (up to 40 mW/cm(2)). The measurements were done in a forward scattering configuration, with simultaneous linear scanning of laser frequency and magnetic field at different temporal rates. The latter revealed, in a single measurement, the dependences of maximum nonlinear Faraday signal and the corresponding B-field on the laser frequency within the Doppler profile.

Journal Article↗
PubMed1995

[Experiments aimed at developing an implantable and continuously functioning glucose sensors based on polarimetry].

In vitro and in vivo experiments devised with the aim of developing a permanently implantable glucose sensor based on polarimetry are described. It was found that in ultrafiltrated human blood plasma the overall optical rotation was 94% specific for glucose, and that polarisation photometry yielded a sufficiently sensitive signal for in vivo glucose detection. The three types of capillary membrane intended for implantation that we tested, revealed an in vitro response time to glucose concentration of 10 minutes; when implanted, they maintain this over a period of weeks, during which time the same glucose concentrations can be measured daily in ultrafiltrated capillary fluid as in the blood of the animals (guinea pigs). The drop in glucose concentration induced 20 minutes after a single administration of insulin can also be detected in both fluids. The experiments described indicate that the development of an implantable polarimetric glucose sensor is possible.

Animals↗
PubMedDate not supplied

Chemical analysis and antimicrobial activity of Halimium voldii.

Volatile constituents and a hexane extract of the leaves of Halimium voldii Kit Tan, Perdetzoglou & Raus, sp. nova, were analyzed by GC and GC-MS. Thirty compounds were identified in the essential oil of Halimium representing 88.7% of the oil composition. The main components were nonanal (12.8%), dodecane (10.6%), Z-caryophyllene (8.2%), gamma-muurolene (10.9%), delta-cadidene (3.5%), caryophyllene oxide (5.1%), beta-eudesmol (3.6%) and manoyl oxide (5.5%). Thymol was identified in the hexane extract as the main compound. A labdane diterpene ent-labd-7, 13 (E)-dien, 15-ol was detected by its mass spectra fragmentation pattern and its structure was determined by spectroscopic methods and its optical rotation. The essential oil and the hexane extract were assayed for their antimicrobial activity against gram (+) and gram (-) bacteria.

Anti-Bacterial Agents↗
PubMed1997

Noninvasive blood glucose monitoring.

The concentration of glucose in the blood may soon be measured noninvasively, without puncturing the finger to obtain a drop of blood. Current prototype devices for this purpose require greater accuracy and miniaturization to be commercially viable. No such device has been approved for marketing by the U.S. Food and Drug Administration. The technology used for noninvasive blood glucose monitoring involves either radiation or fluid extraction. With radiation technology, an energy beam is 1) applied to the body, 2) modified proportionate to the concentration of glucose in the blood, and 3) measured. The blood glucose concentration is then calculated. With fluid extraction technology, a body fluid containing glucose in a concentration proportionate to the blood glucose concentration is extracted and measured. The blood glucose concentration is then calculated. The most promising technologies are 1) near-infrared light spectroscopy, 2) far-infrared radiation spectroscopy, 3) radio wave impedance, 4) optical rotation of polarized light, 5) fluid extraction from skin, and 6) interstitial fluid harvesting. Each method has features predictive of commercial viability, as well as technical problems to overcome.

Blood Glucose↗
PubMedDate not supplied

Synthesis and electrophysiological studies of a novel epibatidine analogue.

The new epibatidine analogue exo-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane (2PABH) was synthesised. Separation of enantiomers was performed on chiral HPLC chromatography in polar-organic phase mode at 0 degree C. Enantiomeric purity was greater than 99.8%ee for the (-)- and 90.5%ee for the (+)-enantiomer respectively. Optical rotation was determined to be [alpha]23D = +/- 13 degrees. Electrophysiological studies of 2PABH were carried out on alpha 4 beta 2, alpha 3 beta 4 and alpha 7 nAChR subtypes cloned from rat and reconstituted in Xenopus oocytes. Both enantiomers could not significantly activate the heteromeric subtypes. The homomeric alpha 7 nAChR displays a high sensitivity only towards (-)-2PABH. The EC50 for (-)-2PABH and ACh were determined (32.5 +/- 9.5 microM, 137.3 +/- 16.5 microM). (-)-2PABH was shown to be a partial agonist (80% of ACh). Thus the efficacy of 2PABH differs markedly from that of epibatidine. The intramolecular N-N-distance and the spatial pyridine nitrogen orientation play a central role in nAChR recognition.

Animals↗
PubMed1999

Physical and chemical properties of molecular compounds of lactose.

The physical and chemical properties of the molecular compounds of lactose 5 alpha-/3 beta- and 3 alpha-/2 beta-lactose were studied. The melting point and the heat of combustion were determined. The specific optical rotation of aqueous and organic solutions of these compounds was measured and was in agreement with their stoichiometric formula. Weak differences were observed in the chromatographic mobility of the lactose molecular compounds provided that nonaqueous solvents were used. The analysis by infrared spectroscopy showed that these compounds were due to association of alpha-lactose and beta-lactose crystals by a specific lattice of hydrogen bonding. The latter could be destroyed under controlled water vapor uptake. These physical and chemical properties led us to hypothesize on the means of association of these molecular compounds by comparison with the known structures of the other crystalline lactose forms.

Calorimetry, Differential Scanning↗
PubMed1989

Cyclopentenoid cyanohydrin glycosides with unusual sugar residues.

The cyclopentenoid cyanohydrin glycosides passicapsin and passibiflorin have been identified as (1S, 4R)-1-(beta-D-glucopyranosyloxy)-4-(2,6-dideoxy-beta-D-xylo-hex o pyranosyloxy)-2-cyclopentene-1-carbonitrile and (1S, 4R)-1-(beta-D-glucopyranosyloxy)-4-(6-deoxy-beta-D-gulopyranosy loxy)-2- cyclopentene-1-carbonitrile, respectively, using one- and two-dimensional NMR spectroscopy, selective acid-catalysed cleavage of the glycosidic linkages of the deoxy sugars, and optical rotation data.

Carbohydrates↗
PubMed1975

Bioconversion of ribostamycin (SF-733). II. Isolation and structure of 3-N-acetylribostamycin, a microbiologically inactive product of ribostamycin produced by Streptomyces ribosidificus.

The isolation and structure determination of 3-N-acetylribostamycin, a microbiologically inactive derivative, produced enzymatically from ribostamycin by Streptomyces ribosidificus is described. The location of the acetyl group was established by mass and NMR spectrometry of the new compound and its derivatives, and by optical rotation studies conducted on N-ethoxycarbonyl-2-deoxystreptamine. The latter compound was obtained by partial acid hydrolysis of tri-N-ethoxycarbonyl-N-acetylribostamycin.

Acetyltransferases↗
PubMed1976

Microbial transformation of daunomycinone by Streptomyces aureofaciens B-96.

Daunomycinone, aglycone of the anthracycline antibiotic daunomycin, was transformed by a washed mycelia of Streptomyces aureofaciens B-96 in a buffer solution containing sucrose; the obtained product, dihydrodaunomycinone (9-(1-hydroxyethyl)-7,8,9,10-tetrahydro-6,7,9,11-tetrahydroxy-4-methoxy-5,12-naphthacenequinone), was identified by measuring basic physicochemical characteristics (IR, UV and visible spectra, mass spectra and NMR, optical rotation and m.p.).

Biotransformation↗
PubMed1976

The constituent amino acids and fatty acid of antibiotic 333-25. (Studies on antibiotics from the genus Bacillus. XII.

Measurement of the optical rotational activities of the constituent amino acids of antibiotic 333-25 identified 2,4-diaminobutyric acid (D-form 1, L-form 4), L-leucine (2) and D-phenylalanine (1). The fatty acid constituent was determined to be beta-hydroxy anteisononanoic acid by gas chromatography, nuclear magnetic resonance and mass spectra. Differentiation from the structure of antibiotic EM 49 is discussed.

Amino Acids↗
PubMed1980

Milbemycins, a new family of macrolide antibiotics: fermentation, isolation and physico-chemical properties.

A search for novel insecticides has yielded the milbemycins, a new family of macrolide antibiotics with insecticidal and acaricidal activity. They are produced in submerged cultures of Streptomyces hygroscopicus subsp. aureolacrimosus. Fermentation studies on the strain were conducted in shaken flasks and 30-liter jar fermentors. From the culture broth 13 milbemycins were purified to homogeneity by column and thin-layer chromatography on silica gel and alumina. Physico-chemical data, such as mass spectra, UV and IR absorption spectra, optical rotations and melting points of the milbemycins are described.

Anti-Bacterial Agents↗
PubMed1983

Epimerization and stereochemistry of avoparcin.

The epimerization of avoparcin entities is discussed in some detail. The absolute stereochemistry of avoparcin is now known since the N-methyl terminal amino acid of the aglycone has been isolated and shown to exhibit negative optical rotation and hence has the R-configuration. The same amino acid has been isolated from an epimerized solution of avoparcin and found to have positive rotation and hence the S-configuration. A comparison is made of the CD curves of beta-avoparcin and epi-beta-avoparcin. Some discussion on the effect of protonation of the terminal N-methyl group on the antibacterial activity of avoparcin is included.

Anti-Bacterial Agents↗