Investigation on the Heats of Combustion of 'Proposed Secondary Standard Substances and on Position and Optical Isomers

1927 ◽  
Vol 31 (1) ◽  
pp. 58-68 ◽  
Author(s):  
L. J. P. Keffler ◽  
F. C. Guthrie
Keyword(s):  
Secondary Standard ◽  
Optical Isomers ◽  
Heats Of Combustion

Refutation of alleged differences in the energy contents of optical isomers

1969 ◽  
Vol 47 (2) ◽  
pp. 79-83 ◽  
Author(s):  
Erich Baer ◽  
Hans-Helmut Flehmig
Keyword(s):  
Hydrogen Chloride ◽  
Gaseous Hydrogen ◽  
Optical Isomers ◽  
Heats Of Combustion ◽  
Experimental Values ◽  
Related Compounds

The heats of combustion of the optical isomers of α-monostearin and of glyceraldehyde reported by D. Buchnea to differ by 62 and 64 kcal/g-mole, respectively, were redetermined. Our experimental values for these, and for the optical isomers of several related compounds, are in accord with the generally accepted view that the heats of combustion of optical isomers are identical. They refute not only Buchnea's concept of different energy contents for optical isomers, but also the claim that they are responsible for the different rates of reaction observed by him for L-, D-, and DL-α-monostearin in ethereal suspensions containing gaseous hydrogen chloride.

A COMPARISON BETWEEN THE EXOPHTHALMOS INHIBITING EFFECTS OF SODIUM-D- AND SODIUM-L-THYROXINE IN GUINEA PIGS

1962 ◽  
Vol 41 (4) ◽  
pp. 619-624 ◽  
Author(s):  
Björn Tengroth ◽  
Uno Zackrisson
Keyword(s):  
Hyaluronic Acid ◽  
Pituitary Gland ◽  
Guinea Pigs ◽  
Anterior Lobe ◽  
Optical Isomers ◽  
Connective Tissues ◽  
Response Curves ◽  
Experimental Animals ◽  
Inhibiting Effect ◽  
Caloric Effect

ABSTRACT The general change in the connective tissues which occurs in animals with experimentally produced exophthalmos, consists in an increase in the amount of hyaluronic acid, which binds the water in the connective tissue. Many regard this process as a stimulation of the mucinous system in the connective tissues, and consider this an explanation of the phenomenon of exophthalmos. When the experimental animals are injected with thyroxine or thyroid extract, the reaction observed is opposite to that seen following the injection of the anterior lobe of the pituitary gland. In the former case, there is a reduction in the amount of hyaluronic acid and consequently a decrease in the water content in the connective tissues. In the experiments in question, Na-d-thyroxine and Na-l-thyroxine), in crystalline form, were tested for their inhibiting effect on the development of exophthalmos in experimental animals. The animals used were male albino guinea-pigs. An extract of the anterior lobe of the pituitary gland (TSH Organon)) was used to produce exophthalmos. In previous work (Tengroth 1961), it was shown, using an X-ray measuring technique, that d-thyroxine, despite its poor caloric effect, like l-thyroxine had an exophthalmos-inhibiting effect. When comparing the dose-response curves of the exophthalmos-inhibiting properties of both these optical isomers, it appears that d-thyroxine has an inhibiting effect which is significantly greater than that of l-thyroxine. The significance of this observation is discussed.

Separation and Characterization of Standard Propoxyphene Diastereomers and Their Determination in Pharmaceutical and Illicit Preparations

1981 ◽  
Vol 64 (4) ◽  
pp. 875-883
Author(s):  
Shiv K Soni ◽  
Daniel Van Gelder
Keyword(s):  
High Pressure ◽  
Optical Isomers ◽  
Gold Chloride ◽  
Melting Points ◽  
Eutectic Melting ◽  
Racemic Mixtures ◽  
The Individual ◽  
Isomeric Mixtures ◽  
Asymmetric Carbon

Abstract Due to the existence of 2 asymmetric carbon atoms in: the propoxyphene molecule, there are 4 diastereomers: alpha dextro, alpha levo, beta dextro, and beta levo. Only α-d-propoxyphene is included under the federal Controlled Substances Act. Baseline separations of propoxyphene from various incipients (aspirin, caffeine, phenacetin, and acetaminophen) present in pharmaceutical and illicit preparations, and between the alpha and beta diastereomers, were achieved by high pressure liquid chromatography. The column eluant was collected and propoxyphene was extracted. The optical isomers were differentiated and characterized by melting points and by chemical microcrystalline tests. Using hot stage thermomicroscopy, the eutectic melting points of binary isomeric mixtures of propoxyphene bases and salts were found to be depressed about 10° and 15-30°C, respectively, below the individual isomer melting points. The characteristic microcrystals formed with the alpha racemic mixtures by using a glycerin-aqueous gold chloride reagent were not produced by the beta racemic mixtures.

scholarly journals Role of Chiral Configuration in the Photoinduced Interaction of D- and L-Tryptophan with Optical Isomers of Ketoprofen in Linked Systems

2021 ◽  
Vol 22 (12) ◽  
pp. 6198
Author(s):  
Aleksandra A. Ageeva ◽  
Ilya M. Magin ◽  
Alexander B. Doktorov ◽  
Victor F. Plyusnin ◽  
Polina S. Kuznetsova ◽  
...  
Keyword(s):  
Amino Acid ◽  
Excited States ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Dipole Interaction ◽  
The Body ◽  
Model Systems ◽  
Optical Isomers ◽  
Amino Acid Properties ◽  
Parkinson’S Diseases

The study of the L- and D-amino acid properties in proteins and peptides has attracted considerable attention in recent years, as the replacement of even one L-amino acid by its D-analogue due to aging of the body is resulted in a number of pathological conditions, including Alzheimer’s and Parkinson’s diseases. A recent trend is using short model systems to study the peculiarities of proteins with D-amino acids. In this report, the comparison of the excited states quenching of L- and D-tryptophan (Trp) in a model donor–acceptor dyad with (R)- and (S)-ketoprofen (KP-Trp) was carried out by photochemically induced dynamic nuclear polarization (CIDNP) and fluorescence spectroscopy. Quenching of the Trp excited states, which occurs via two mechanisms: prevailing resonance energy transfer (RET) and electron transfer (ET), indeed demonstrates some peculiarities for all three studied configurations of the dyad: (R,S)-, (S,R)-, and (S,S)-. Thus, the ET efficiency is identical for (S,R)- and (R,S)-enantiomers, while RET differs by 1.6 times. For (S,S)-, the CIDNP coefficient is almost an order of magnitude greater than for (R,S)- and (S,R)-. To understand the source of this difference, hyperpolarization of (S,S)-and (R,S)- has been calculated using theory involving the electron dipole–dipole interaction in the secular equation.

scholarly journals TRYPTOPHAN REQUIREMENT FOR GROWTH AND UTILIZATION OF ITS OPTICAL ISOMERS

1952 ◽  
Vol 196 (1) ◽  
pp. 33-43
Author(s):  
M. Jane Oesterling ◽  
William C. Rose
Keyword(s):  
Optical Isomers

scholarly journals Enantioenriched Positive Allosteric Modulators Display Distinct Pharmacology at the Dopamine D1 Receptor

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3799
Author(s):  
Tim J. Fyfe ◽  
Peter J. Scammells ◽  
J. Robert Lane ◽  
Ben Capuano
Keyword(s):  
Dopamine D1 Receptor ◽  
D1 Receptor ◽  
Intrinsic Activity ◽  
Optical Isomers ◽  
Allosteric Modulators ◽  
Disease States ◽  
Starting Point ◽  
Significant Difference ◽  
Optically Pure ◽  
Allosteric Properties

(1) Background: Two first-in-class racemic dopamine D1 receptor (D1R) positive allosteric modulator (PAM) chemotypes (1 and 2) were identified from a high-throughput screen. In particular, due to its selectivity for the D1R and reported lack of intrinsic activity, compound 2 shows promise as a starting point toward the development of small molecule allosteric modulators to ameliorate the cognitive deficits associated with some neuropsychiatric disease states; (2) Methods: Herein, we describe the enantioenrichment of optical isomers of 2 using chiral auxiliaries derived from (R)- and (S)-3-hydroxy-4,4-dimethyldihydrofuran-2(3H)-one (d- and l-pantolactone, respectively); (3) Results: We confirm both the racemate and enantiomers of 2 are active and selective for the D1R, but that the respective stereoisomers show a significant difference in their affinity and magnitude of positive allosteric cooperativity with dopamine; (4) Conclusions: These data warrant further investigation of asymmetric syntheses of optically pure analogues of 2 for the development of D1R PAMs with superior allosteric properties.

scholarly journals Approbation of the Laser Doppler Anemometer Lad-08 on the Secondary Standard Test Rig for Air Flow Speed

2020 ◽  
Vol 1675 ◽  
pp. 012082
Author(s):  
I K Kabardin ◽  
V G Meledin ◽  
S V Dvoinishnikov ◽  
V A Pavlov ◽  
G V Bakakin ◽  
...  
Keyword(s):  
Air Flow ◽  
Flow Speed ◽  
Standard Test ◽  
Laser Doppler Anemometer ◽  
Laser Doppler ◽  
Secondary Standard ◽  
Test Rig
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