Structure dependent regularities of zero-point plus heat content energies in organic molecules

1988 ◽  
Vol 66 (2) ◽  
pp. 300-303 ◽  
Author(s):  
S. Fliszár ◽  
F. Poliquin ◽  
I. Bǎdilescu ◽  
E. Vauthier
Keyword(s):  
Harmonic Oscillator ◽  
Organic Molecules ◽  
Heat Content ◽  
Zero Point ◽  
Structural Features ◽  
Harmonic Oscillator Approximation ◽  
Additivity Rules

A representative collection of heat content plus zero-point energies deduced in the harmonic oscillator approximation suggests a number of simple additivity rules which allow ZPE + (HT − H0) to be related to structural features. Accurate evaluations are obtained for alkanes, alkenes, alkynes, cycloalkanes, chloroalkanes, and amines, as well as for large and small cycloalkanes in which CH2 is replaced by O.

scholarly journals Nitrido Technetium-99 m Core in Radiopharmaceutical Applications: Four Decades of Research

Inorganics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 3 ◽  
Author(s):  
Bolzati ◽  
Dolmella
Keyword(s):  
Nuclear Medicine ◽  
Organic Molecules ◽  
Single Photon ◽  
Photon Emission ◽  
Structural Features ◽  
Small Organic Molecules ◽  
Design And Synthesis ◽  
Nitrido Complexes ◽  
Close Relationship ◽  
Relevant Role

The knowledge on element 43 (Tc) of the periodic table, built over the years through the contributions given by the close relationship between chemistry and nuclear medicine, allowed the development of new and increasingly effective radiopharmaceuticals useful both as perfusion and target specific imaging agents for SPECT (single photon emission tomography). Among the manifold Tc-compounds, Tc(V) nitrido complexes played a relevant role in the search for new technetium-99m radiopharmaceuticals, providing efficient labeling procedures that can be conveniently exploited for the design and synthesis of agents, also incorporating small organic molecules or peptides having defined structural features. With this work, we present an overview of four decades of research on the chemistry and on the nuclear medicine applications of Tc(V) nitrido complexes.

scholarly journals Bombyx mori Silk Fibroin Regeneration in Solution of Lanthanide Ions: A Systematic Investigation

2021 ◽  
Vol 9 ◽  
Author(s):  
Giorgio Rizzo ◽  
Marco Lo Presti ◽  
Cinzia Giannini ◽  
Teresa Sibillano ◽  
Antonella Milella ◽  
...  
Keyword(s):  
Bombyx Mori ◽  
Silk Fibroin ◽  
Organic Molecules ◽  
Structural Features ◽  
Systematic Investigation ◽  
Lanthanide Ions ◽  
Ordered Structure ◽  
Disordered Structures ◽  
Chaotropic Salts ◽  
Bombyx Mori Silk

Silk Fibroin (SF) obtained from Bombyx mori is a very attractive biopolymer that can be useful for many technological applications, from optoelectronics and photonics to biomedicine. It can be processed from aqueous solutions to obtain many scaffolds. SF dissolution is possible only with the mediation of chaotropic salts that disrupt the secondary structure of the protein. As a consequence, recovered materials have disordered structures. In a previous paper, it was shown that, by modifying the standard Ajisawa’s method by using a lanthanide salt, CeCl3, as the chaotropic agent, it is possible to regenerate SF as a fibrous material with a very ordered structure, similar to that of the pristine fiber, and doped with Ce+3 ions. Since SF exhibits a moderate fluorescence which can be enhanced by the incorporation of organic molecules, ions and nanoparticles, the possibility of doping it with lanthanide ions could be an appealing approach for the development of new photonic systems. Here, a systematic investigation of the behavior of degummed SF in the presence of all lanthanide ions, Ln+3, is reported. It has been found that all lanthanide chlorides are chaotropic salts for solubilizing SF. Ln+3 ions at the beginning and the end of the series (La+3, Pr+3, Er+3, Tm+3, Yb+3, Lu+3) favor the reprecipitation of fibrous SF as already found for Ce+3. In most cases, the obtained fiber preserves the morphological and structural features of the pristine SF. With the exception of SF treated with La+3, Tm+3, and Lu+3, for all the fibers re-precipitated a concentration of Ln+3 between 0.2 and 0.4% at was measured, comparable to that measured for Ce+3-doped SF.

New methods of identifying organic compounds

1979 ◽  
Vol 293 (1400) ◽  
pp. 157-166 ◽  
Keyword(s):  
Organic Molecules ◽  
Ion Beam ◽  
Structural Features ◽  
Ion Source ◽  
Side Chain ◽  
Fragmentation Pattern ◽  
Electric Sector ◽  
Ion Structure ◽  
New Methods ◽  
Free Region

A 'reversed' geometry mass spectrometer, in which the ion beam passes through the magnetic sector before the electric sector, offers several advantages for the study of large organic molecules. The method used is to select individual ionic species formed in the ion source in turn by using the magnet and to study the fragmentation of these species in the field-free region in front of the electric sector. Either unimolecular or collision-induced fragmentations can be investigated, the masses of the daughter species being determined by scanning the electric sector. By selecting a variety of individual ions, a comprehensive fragmentation ‘ map' of the molecular species can be constructed. Because it is a voltage that is scanned, the instrument can readily be computer controlled which gives improved reproducibility of scanning, together with other advantages. The several pathways that often link a particular fragment ion with the molecular ion provide complementary information concerning ion structure. The fragmentation pattern of any ion is often sufficiently characteristic of the ion structure to allow direct identification of structural features present to be made by comparing the pattern from the relevant ion with that of an ion formed from a known reference compound. By using these methods the molecular structure of large organic molecules can often be deduced. Large isomeric molecules such as steroids, differing only in the structure of a side chain, can be distinguished by selecting only ions containing the side chain for study. The new methods also offer advantages for the detection and identification of individual components in mixtures.

The Influence of Molecular Vibration on Brayton-Cycle Performance

1962 ◽  
Vol 29 (2) ◽  
pp. 396-398
Author(s):  
T. A. Jacobs ◽  
J. R. Lloyd
Keyword(s):  
Harmonic Oscillator ◽  
Cycle Performance ◽  
Molecular Vibration ◽  
Brayton Cycle ◽  
Harmonic Oscillator Approximation

By means of the harmonic-oscillator approximation, the influence of molecular vibration on Brayton-cycle performance is demonstrated.

Protons, osmolytes, and fitness of internal milieu for protein function

1986 ◽  
Vol 251 (2) ◽  
pp. R197-R213 ◽  
Author(s):  
G. N. Somero
Keyword(s):  
Intracellular Ph ◽  
Protein Function ◽  
Organic Molecules ◽  
Structural Features ◽  
Internal Milieu ◽  
Inorganic Ion ◽  
Metabolic Functions ◽  
Optimal Values ◽  
High Level ◽  
Intracellular Milieu

The composition of the intracellular milieu shows striking similarities among widely different species. Only certain values of intracellular pH, values that generally reflect alphastat regulation, and only narrow ranges of inorganic ion concentrations are found in the cytoplasm of the cells of most animals, plants, and microorganisms. In water-stressed organisms only a few types of low-molecular-weight organic molecules (osmolytes) are accumulated. These highly conserved characteristics of the intracellular fluids reflect the need to maintain critical features of macromolecules within narrow ranges optimal for life. For proteins these features include maintaining adequate rates of catalysis, a high level of regulatory responsiveness, and a precise balance between stability and lability of structure (tertiary conformation, subunit assembly, and multiprotein complexes). The optimal values for these functional and structural features of proteins often lie near the midrange of possible values for these properties, and only under specific conditions of intracellular pH, ionic strength, and osmolyte composition are these optimal midrange values conserved. In dormant cells the departure of solution conditions from values that are optimal for protein function and structure may be instrumental in reducing or shutting down metabolic functions. Seen from a broad evolutionary perspective, the evolution of the intracellular milieu is an important complement to macromolecular evolution. In certain instances appropriate modifications of the internal milieu may reduce the need for adaptive amino acid replacements in proteins.

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