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At least 91 records · Page 5Linked to original sources
PubMed2005

Conformational effects on optical rotation. 2-Substituted butanes.

The specific rotations of 2-substituted butanes (X = F, Cl, CN, and HCC) were calculated at the B3LYP/aug-cc-pVDZ level as a function of the C-C-C-C torsion angle. The results for the four compounds are remarkably similar, despite large differences in the electronic transition energies. The temperature dependence of the specific rotations for 2-methylbutyronitrile and for 2-chlorobutane was studied to give experimental information about the effect of the torsion angle on the specific rotation. The results were in good accord with B3LYP/aug-cc-pVDZ calculations. The specific rotations derived from the study of 2-chlorobutane are similar to those previously obtained for 3-chloro-1-butene, indicating that the double bond does not have a large effect on the optical rotations, but it did lead to a large difference between calculated and observed specific rotations.

Journal Article↗
PubMed1999

Hemorheology and tissue oxygenation in hypertensives with lipoidoproteinosis and peripheral occlusive arterial disease (POAD) treated with sulodexide and pravastatine and evaluated with laser assisted optical rotational red cell analyzer (LORCA) and transcutaneous oxymetry.

BACKGROUND: During arterial hypertension it is often possible to find other factors like lipoidoproteinosis and peripheral arterial disease (POAD), which can accentuate blood rheological abnormalities in hypertensive subjects. A group of hypertensives with lipoidoproteinosis (LP) and POAD were therefore examined to evaluate the relationship between these factors and blood rheological disorders and, if possible, to correct it. METHODS: We studied a group of 27 hypertensives with LP and POAD (15 males and 12 females in menopause for at least 1 year, aged 48 +/- 4 years), with WHO stage I hypertension, obesity (BMI = 30 +/- 2), stage II type "a" POAD, class 2 type "b" lipoidoproteinosis (acc. to Fredrick-son's classification) and hyperfibrinogenemia. All patients received oral medication with 500 lipidic units (ULS) sulodexide a day, 20 mg pravastatin o.d. orally, and were put on a low-salt and low-calorie diet (1400 kcal/day) during a follow-up of 60 days. Blood rheology status was evaluated before and after treatment (red blood cell--RBC--deformability and aggregability) using a new computerized instrument, which uses laser rays: the laser assisted optical rotational red cell analyzer (LORCA) (acc. to Hardeman) and RBC deformability using optical microscopy under immersion (acc. to Zipursky and Forconi). Transcutaneous oxymetry was also used to evaluate tissue oxygenation. RESULTS AND CONCLUSIONS: At the end of the study a significant improvement (p < 0.01) was noted in the blood rheological patterns of peripheral perfusion and tissue oxygenation. This underlined the positive influence of sulodexide with pravastatin in improving hemorheological patterns and modulating hypercholesterolemia and hyperfibrogenemia in hypertensives with POAD II "a" and LP 2 "b" and blood rheology disorders.

Adult↗
PubMed2006

Coupled cluster and density functional theory studies of the vibrational contribution to the optical rotation of (S)-propylene oxide.

In a previous study (Chemical Physics Letters 2005, 401 , 385) we computed the optical rotatory dispersion of (S)-propylene oxide in gas phase and solution using the hierarchy of coupled cluster models CCS, CC2, CCSD, and CC3. Even for the highly correlated CC3 model combined with a flexible basis set, the theoretical gas-phase specific rotation at 355 nm was found to be negative in contrast to the experimental result. We argued that vibrational contributions could be crucial for obtaining a complete understanding of the experimental result. Here, we show that this indeed is the case by using coupled cluster models and density functional theory methods to calculate the vibrational contributions to the gas-phase specific rotation at 355, 589.3, and 633 nm. While density functional theory (B3LYP and SAOP functionals) overestimates the specific rotation at 355 nm by approximately 1 order of magnitude and yields an incorrect sign at 589.3 and 633 nm, the coupled cluster results are in excellent agreement with the experimentally measured optical rotations. We find that all vibrational modes contribute significantly to the optical rotation and that temperature effects must be taken into account.

Journal Article↗
PubMed2000

Binocular neurons in the nucleus lentiformis mesencephali in pigeons: responses to translational and rotational optic flowfields.

The pretectal nucleus lentiformis mesencephali (LM) receives direct input from the contralateral retina and is dedicated to the analysis of optic flowfields resulting from self-motion. The activity of 126 LM neurons in response to optic flow stimuli was recorded. As with previous studies, it was found that most neurons (approximately 90%) exhibited direction-selectivity to large-field stimuli moving in the contralateral hemifield. However, some neurons (approximately 10%) responded to stimulation of both eyes and had receptive field structures conducive for detection of particular patterns of optic flow resulting from either self-translation or self-rotation. These binocular neurons were maximally responsive to panoramic optic flowfields simulating either translational or rotational optic flow.

Animals↗
PubMed2002

Enantioselective synthesis of (-)-terpestacin and (-)-fusaproliferin: clarification of optical rotational measurements and absolute configurational assignments establishes a homochiral structural series.

An enantioselective synthesis of the syncytium formation inhibitor (-)-terpestacin (1, 19 steps, 5.8% yield from the allylation product of (R,R)-pseudoephedrine propionamide, 3) and the fungal metabolite (-)-fusaproliferin (2, 21 steps, 5.3% yield from 3) in their natural configurations is described. The route employs a series of stereoselective enolate alkylation reactions to establish the initial stereogenic center, set the quaternary carbon configuration, close the 15-membered ring, and introduce the side-chain residue with proper stereocontrol. Careful analysis of our synthetic materials alongside natural samples has revealed that several errors were made in the earlier measurements of optical rotation or in the absolute stereochemical assignments of these natural products. Clarifying all discrepancies, we show here that natural terpestacin (1) is levorotatory, not dextrorotatory as originally described, but was correctly assigned as the (1S,11S,15R,23S)-enantiomer. Fusaproliferin (2) is levorotatory, as reported, but is in fact the (1S,11S,15R,23S)-enantiomer and not the antipodal configuration originally assigned.

Anti-Bacterial Agents↗
PubMed2005

Tuning the CD spectrum and optical rotation value of a new binaphthalene molecule with two spiropyran units: mimicking the function of a molecular "AND" logic gate and a new chiral molecular switch.

With the view to developing new chiral molecular switches and logic gates, a new binaphthalene molecule with two spiropyran units (1) was synthesized and characterized. Absorption and 1H NMR spectral studies of 1 after reaction with acid/base indicate acidichromism can occur to compound 1. The synergistic actions of acid and UV light irradiation result in a remarkable change for the CD spectrum of the relatively dilute solution of 1, mimicking the behavior of a chiral "AND" gate, since the "ouput" is the CD signal. Furthermore, the optical rotation value of the relatively concentrated solution of 1 can be reversibly tuned after sequential reactions with acid and base, and thus a chiral molecular switch with nondestructive "output" signal is realized. The present results not only add a new example of chiral molecular switch with nondestructive readout but also provide a chiral "AND" gate based on the axial chiral binaphthalene to which switchable units are linked.

Journal Article↗
PubMed2001

Hepatitis C virus core particle detected by immunoelectron microscopy and optical rotation technique.

Hepatitis C Virus (HCV) are 55-65 nm spherical particles, but the internal structure of the virion remains to be clarified. To clarify the morphology of HCV core particles, we performed an immune electron microscopy (IEM) using plasma samples from two blood donors with high HCV RNA titers and a detergent-treated anti-HCV core antibody-free plasma sample with high HCV RNA titer (1.5x10(8) copies/ml). Spherical particles, with 33-40 nm in diameter (an average diameter of 37 nm) were found in 1.22-1.25 g/ml fractions after sucrose density gradient centrifugation by conventional electron microscopy (EM). IEM using rabbit polyclonal antibody (RR8) specific to the putative HCV core protein and goat anti-rabbit IgG colloidal gold particles revealed that these spherical particles specifically reacted with RR8. This finding indicates that the spherical particles are naked HCV core particles. Some of the HCV core particles had an icosahedron-like structure. Optical rotation technique showed that the HCV core particle exhibits six-fold symmetry and that the length of regular hexagon side is approximately 20 nm. These findings showed that HCV core particles are spherical particles of 33-40 nm in diameter and that HCV core particles may possess an icosahedron-like structure and a buoyant density of 1.22-1.25 g/ml.

Journal Article↗
PubMed1998

Common reference frame for neural coding of translational and rotational optic flow.

Self-movement of an organism through the environment is guided jointly by information provided by the vestibular system and by visual pathways that are specialized for detecting 'optic flow'. Motion of any object through space, including the self-motion of organisms, can be described with reference to six degrees of freedom: rotation about three orthogonal axes, and translation along these axes. Here we describe neurons in the pigeon brain that respond best to optic flow resulting from translation along one of the three orthogonal axes. We show that these translational optic flow neurons, like rotational optic flow neurons, share a common spatial frame of reference with the semicircular canals of the vestibular system. The three axes to which these neurons respond best are the vertical axis and two horizontal axes orientated at 45 degrees to either side of the body midline.

Animals↗