scholarly journals OPTICAL ROTATION AND HELICAL POLYPEPTIDE CHAIN CONFIGURATION IN COLLAGEN AND GELATIN

1955 ◽  
Vol 1 (3) ◽  
pp. 203-214 ◽  
Author(s):  
Carolyn Cohen
Keyword(s):  
Optical Activity ◽  
Optical Rotation ◽  
Specific Rotation ◽  
X Ray Diffraction ◽  
Citrate Buffer ◽  
Gelatin Films ◽  
Dispersion Data ◽  
Single Term ◽  
Native Collagen ◽  
Helical Configuration

The optical rotation phenomena exhibited by a citrate-extracted fraction of ichthyocol (from carp swim bladder), as well as by the parent gelatin derived therefrom, have been studied. Dispersion data for all cases follow a single-term Drude equation, but the variations with state are adequately expressed by simple reference to changes in [α]D as follows:— 1. The native collagen fraction, dispersed in 0.15 M citrate buffer at pH 3.7 in the cold (11°C.), yields a high negative specific rotation, [α]D, near –350°. 2. During equilibration at 40°C., which causes conversion to a monodisperse parent gelatin, the rotation drops to about –110°. 3. Gelation at 2°C. results in a partial regain of rotation to around –290°. This mutarotation is reversible, depending on temperature. 4. In the range 0.02 to 0.28 per cent the native ichthyocol and the warm gelatin solutions show little concentration dependence, but with the cold gelatin solutions the specific rotation increases with concentration. Gelatin films formed by cold evaporation yield high specific rotation (ca. –620°), but those formed by hot evaporation retain low optical activity. 5. Since this same collagen-gelatin system has been investigated physicochemically, it is possible to relate molecular changes to the observed variations in optical rotation. Conclusions are similar to those of Robinson (1953), who studied other gelatins: high negative rotation is believed related to a native collagen polypeptide configuration, herein specified as helical (from x-ray diffraction considerations) and destroyed by heating. The possible roles of intermolecular interactions and of prevalent pyrrolidine constituents in influencing the helical configuration and optical activity are discussed.

scholarly journals Optical rotatory power. I—A theoretical calculation for a molecule containing only isotropic refractive centres

1934 ◽  
Vol 144 (853) ◽  
pp. 655-675 ◽  
Keyword(s):  
Theoretical Calculation ◽  
Optical Activity ◽  
Chemical Structure ◽  
Central Atom ◽  
Optical Rotation ◽  
Rotatory Power ◽  
Theoretical Formula ◽  
Optical Rotatory ◽  
Present Communication ◽  
Optical Rotatory Power

Ever since the time of van’t Hoff and Le Bel the number investigations dependent on optical activity, or attempting to elucidate optical activity, has been very great, and it is remarkable that, even at the present time, there is no theoretical formula which gives the relation between the magnitude of the rotation and the chemical structure of the molecule concerned. The present communication supplies this want with regard to the molecule of the simplest asymmetric type: the molecule with four different groups attached to one central atom. Various special hypothese have been postulated to explain optical activity, but a few investigators have shown quite definitely that there is no necessity for any of these hypotheses. Born* and Oseen have shown independently that, if the molecule has a dissymmetric structure, the ordinary refractive properties of the atoms will account for an optical rotation. Gray* and de Mallemann have attempted calculations of formulæ for optical retatory power on this basis. However, it has not been possible to condense the numerous algebraic terms which occur in these calculaations into a compact form.

scholarly journals Enhanced gyrotropic birefringence and natural optical activity on electromagnon resonance in a helimagnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. Iguchi ◽  
R. Masuda ◽  
S. Seki ◽  
Y. Tokura ◽  
Y. Takahashi
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Optical Activity ◽  
Optical Rotation ◽  
Magnetoelectric Coupling ◽  
Optically Active ◽  
Crystalline Solid ◽  
Spin Order ◽  
Active Devices ◽  
Principal Axes

AbstractSpontaneous symmetry breaking in crystalline solid often produces exotic nonreciprocal phenomena. As one such example, the unconventional optical rotation with nonreciprocity, which is termed gyrotropic birefringence, is expected to emerge from the magnetoelectric coupling. However, the fundamental nature of gyrotropic birefringence remains to be examined. Here w`e demonstrate the gyrotropic birefringence enhanced by the dynamical magnetoelectric coupling on the electrically active magnon resonance, i.e. electromagnon, in a multiferroic helimagnet. The helical spin order having both polarity and chirality is found to cause the giant gyrotropic birefringence in addition to the conventional gyrotropy, i.e. natural optical activity. It is demonstrated that the optical rotation of gyrotropic birefringence can be viewed as the nonreciprocal rotation of the optical principal axes, while the crystallographic and magnetic anisotropies are intact. The independent control of the nonreciprocal linear (gyrotropic birefringence) and circular (natural optical activity) birefringence/dichroism paves a way for the optically active devices.

Rubescins F–H, new vilasinin-type limonoids from the leaves of Trichilia rubescens (Meliaceae)

2019 ◽  
Vol 74 (7-8) ◽  
pp. 175-182
Author(s):  
Armelle Tontsa Tsamo ◽  
Julio Issah Mawouma Pagna ◽  
Pamela Kemda Nangmo ◽  
Pierre Mkounga ◽  
Hartmut Laatsch ◽  
...  
Keyword(s):  
Ab Initio ◽  
Methylene Chloride ◽  
High Resolution Mass Spectrometry ◽  
Optical Rotation ◽  
Cyclopropane Ring ◽  
Dispersion Data ◽  
Rotation Dispersion ◽  
Oxetane Ring ◽  
Related Compounds ◽  
Potential Precursor

Abstract Three new limonoids, designated as rubescins F (1), G (2), and H (3), together with two known compounds of this type, TS1 (4) and trichirubine A (5), were isolated from methylene chloride/methanol extracts of Trichilia rubescens leaves. The structures of these compounds were elucidated based on 1D and 2D nuclear magnetic resonance (NMR) analysis and complemented by electrospray ionization high-resolution mass spectrometry results and by comparison to data of related compounds described in the literature and ab initio calculations. Rubescin F (1) is the first limonoid from Trichilia spp. with an oxetane ring between C-7 and C-14, which seems to be formed by the isomerization of TS1 (4). The γ-hydroxybutenolide rubescin G (2) is a potential precursor of trichirubine A (5), whereas rubescin H (3) is the first example of a triterpenoid with a single bond between C-7/C-14, forming a cyclopropane ring. The absolute configuration of these limonoids was derived from biosynthetic considerations and ab initio calculations of NMR and optical rotation dispersion data.

scholarly journals Comparison of the Structural Characteristics of Native Collagen Fibrils Derived from Bovine Tendons Using Two Different Methods: Modified Acid-Solubilized and Pepsin-Aided Extraction

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 358 ◽  
Author(s):  
Haiyan Ju ◽  
Xiuying Liu ◽  
Gang Zhang ◽  
Dezheng Liu ◽  
Yongsheng Yang
Keyword(s):  
Type I Collagen ◽  
Structural Characteristics ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Dry Weight ◽  
Collagen Fibrils ◽  
Type I ◽  
X Ray Diffraction ◽  
Aggregation Structure ◽  
Native Collagen

Native collagen fibrils (CF) were successfully extracted from bovine tendons using two different methods: modified acid-solubilized extraction for A-CF and pepsin-aided method for P-CF. The yields of A-CF and P-CF were up to 64.91% (±1.07% SD) and 56.78% (±1.22% SD) (dry weight basis), respectively. The analyses of both amino acid composition and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that A-CF and P-CF were type I collagen fibrils. Both A-CF and P-CF retained the intact crystallinity and integrity of type I collagen’s natural structure by FTIR spectra, circular dichroism spectroscopy (CD) and X-ray diffraction detection. The aggregation structures of A-CF and P-CF were displayed by UV–Vis. However, A-CF showed more intact aggregation structure than P-CF. Microstructure and D-periodicities of A-CF and P-CF were observed (SEM and TEM). The diameters of A-CF and P-CF are about 386 and 282 nm, respectively. Although both A-CF and P-CF were theoretically concordant with the Schmitt hypothesis, A-CF was of evener thickness and higher integrity in terms of aggregation structure than P-CF. Modified acid-solubilized method provides a potential non-enzyme alternative to extract native collagen fibrils with uniform thickness and integral aggregation structure.

scholarly journals Twins in YAl3(BO3)4 and K2Al2B2O7 Crystals as Revealed by Changes in Optical Activity

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Johannes Buchen ◽  
Volker Wesemann ◽  
Steffen Dehmelt ◽  
Andreas Gross ◽  
Daniel Rytz
Keyword(s):  
Optical Properties ◽  
Optical Activity ◽  
Nonlinear Optical ◽  
Frequency Conversion ◽  
Optical Rotation ◽  
Visible Spectrum ◽  
Rotatory Power ◽  
Nonlinear Optical Properties ◽  
Crystal Quality ◽  
Optical Rotatory Dispersion

Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl 3 (BO 3 ) 4 (YAB) and K 2 Al 2 B 2 O 7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens.

III.—The Optical Rotation and Cryoscopic Behaviour of Sugars dissolved in (a) Pormamide, (b) Water

1915 ◽  
Vol 35 ◽  
pp. 22-45
Author(s):  
John Edwin Mackenzie ◽  
Sudhamoy Ghosh
Keyword(s):  
Aqueous Solution ◽  
Optical Rotation ◽  
Specific Rotation ◽  
Initial Value ◽  
Other Substances

The optical rotation of a solution of sucrose in water was first measured by Biot (Mém., 1819, ii, 41) in 1819. He introduced the term “optical saccharimetry” for the method of estimation of sugar by measurement of its optical rotation.In 1846, Dubrunfaut (Ann. Chim. Phys., 1846, xviii, 99) observed that the specific rotation of a freshly prepared aqueous solution of glucose decreased from an initial value of about + 110° to a constant value of +52°. The initial value being approximately double the constant value, he called the phenomenon “bi-rotation.” This term proved unsuitable in the case of other substances where a similar change of rotation took place, the initial and final values being rarely in the proportion of 2: 1; hence the expression “multi-rotation” came into use.

scholarly journals Interference-contrast optical activity: a new technique for probing the chirality of anisotropic samples and more

2020 ◽  
Vol 7 (5) ◽  
pp. 192201 ◽  
Author(s):  
R. P. Cameron ◽  
U. Vogl ◽  
N. Trautmann
Keyword(s):  
Pharmaceutical Industry ◽  
Optical Activity ◽  
Optical Rotation ◽  
New Technique ◽  
Future Research ◽  
Linear Birefringence ◽  
New Class ◽  
Potential Applications ◽  
A New Technique ◽  
Chiral Crystals

We introduce interference-contrast optical activity (ICOA) as a new technique for probing the chirality of anisotropic samples and more. ICOA could underpin a new class of ‘chiral microscopes’, with potential applications spanning the range of chirality and beyond. Two possible versions of ICOA are described explicitly; one designed to probe the optical rotation of a transparent sample regardless of the sample’s linear birefringence (ICOA-OR) and another designed to probe gradients in the optical rotation of a transparent sample (ICOA-GOR). Simulated results for α -quartz lead us to suggest that ICOA-GOR might be applied to help monitor the growth of chiral crystals in the pharmaceutical industry. Possible directions for future research are highlighted.

Origin of the optical activity of silver thiogallate

2000 ◽  
Vol 33 (1) ◽  
pp. 126-129 ◽  
Author(s):  
J. Etxebarria ◽  
C. L. Folcia ◽  
J. Ortega
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Room Temperature ◽  
Optical Rotation ◽  
Linear Dichroism ◽  
Optical Data ◽  
Point Dipole ◽  
Reliable Measurement ◽  
Photoelastic Modulator ◽  
Circular Dichroïsm

Using a high-accuracy universal polarimeter, the birefringence and optical activity of AgGaS2have been determined between 300 and 500 K. The optical rotation has been found to be 94° mm−1at room temperature for a wavelength of 632.8 nm. This value is unexpectedly small if compared with values close to 1000° mm−1at 485 nm reported previously. The present optical data are well explained using a point-dipole model for the calculation of the refractive indices and optical activity. The main contributors to the optical rotation are the S atoms. However, these atoms are not at positions especially suitable to promote extremely large gyrations. Consequently, the size of the optical rotation reported before in the blue part of the spectrum is presumably due to the existence of a circular dichroism band close to that region. Using an optical system based on a photoelastic modulator, a strong linear dichroism peak has been measured in the range 450–500 nm. This fact has prevented reliable measurement of the circular dichroism.

Studies of the optically active compounds of Anacardiaceae exudates. II. The action of Alkali on the long-chain alicyclic Keto Alcohol of Tigaso Oil

1958 ◽  
Vol 11 (1) ◽  
pp. 64 ◽  
Author(s):  
LK Dalton ◽  
JA Lamberton
Keyword(s):  
Optical Activity ◽  
Active Compound ◽  
Optical Rotation ◽  
Large Change ◽  
Optically Active ◽  
Bicyclic Compound ◽  
Compound I ◽  
Alcoholic Alkali ◽  
Rapid Reaction ◽  
Long Chain

In cold alcoholic alkali the optically active compound I from Tigaso oil undergoes a rapid reaction which involves loss of its conjugated carbonyl system, and a large change, with inversion, of its optical rotation. The reaction is interpreted as a cyclization and the product is provisionally formulated as a bicyclononane derivative IIa. In hot alcoholic alkali, IIa is not the final product ; the bicyclic compound undergoes further reaction to give a mixture in which the unsaturated monocyclic triketone VII (R=C16H31) appears to predominate, but which probably consists of a mixture of VII and VIII (R=C16H31). These can be hydrogenated to a mixture of saturated monocyclic triketones VII and VIII (R =C16H33). The same hydrogenated triketones are obtained if IIa is first hydrogenated and then heated with alcoholic alkali. These triketones are optically active and by oxidation with hypobromite, or with permanganate and then hypobromite, yield bromoform and the chemically homogeneous tribasic acid IX, which still retains optical activity. The isolation of the saturated hydroxydiketone IIb in 4 per cent, yield from hydrogenated Tigaso oil suggests that 11% is present to that extent in the original oil.

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