Influence of pH and ionic strength on the lysis of Micrococcus luteus cells by hen lysozyme at low (20°C) and high (physiological, 40°C) temperature*

1981 ◽  
Vol 1 (2) ◽  
pp. 119-123 ◽  
Author(s):  
J. Saint-Blancard ◽  
J. P. Maurel ◽  
J. F. Constant ◽  
J. Berthou ◽  
P. Jolles
Keyword(s):  
High Temperature ◽  
Ionic Strength ◽  
Low Temperature ◽  
Micrococcus Luteus ◽  
Ph Domain ◽  
Ph Optimum ◽  
Temperature Form ◽  
Low Ionic Strength ◽  
Influence Of Ph ◽  
High Temperature Form

From isoactivity curves (showing activity as a function of pH and ionic strength) it was found that in the pH domain 6.7–8.6 frequently used in experiments involving hen lysozyme, the pH optimum of lysis of Micrococcus luteus ceils at low ionic strength (0.02–0.05) by the high-temperature form (40°C physiological temperature) was one to two pH units lower than that by the low-temperature form (20°C).

The Application of X-Ray Diffraction at Elevated Temperatures to Study the Mechanism of Formation of Sodium Tripolyphosphate

1961 ◽  
Vol 5 ◽  
pp. 276-284
Author(s):  
E. L. Moore ◽  
J. S. Metcalf
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Amorphous Phase ◽  
Elevated Temperatures ◽  
Sodium Tripolyphosphate ◽  
X Ray Diffraction ◽  
Mechanism Of Formation ◽  
X Ray ◽  
Temperature Form ◽  
High Temperature Form

AbstractHigh-temperature X-ray diffraction techniques were employed to study the condensation reactions which occur when sodium orthophosphates are heated to 380°C. Crystalline Na4P2O7 and an amorphous phase were formed first from an equimolar mixture of Na2HPO4·NaH2PO4 and Na2HPO4 at temperatures above 150°C. Further heating resulted in the formation of Na5P3O10-I (high-temperature form) at the expense of the crystalline Na4P4O7 and amorphous phase. Crystalline Na5P3O10-II (low-temperature form) appears after Na5P3O10-I.Conditions which affect the yield of crystalline Na4P2O7 and amorphous phase as intermediates and their effect on the yield of Na5P3O10 are also presented.

scholarly journals Comparison of the crystal structures of the low- and high-temperature forms of bis[4-(dimethylamino)pyridine]dithiocyanatocobalt(II)

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Christoph Krebs ◽  
Inke Jess ◽  
Christian Näther
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Three Dimensional ◽  
Monoclinic Space Group ◽  
Temperature Form ◽  
Dimensional Network ◽  
High Temperature Form

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-dimethylaminopyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thiocyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C—H...S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C—H...S and C—H...N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.457 g cm−3) is lower than that of the low-temperature form II (ρ = 1.462 g cm−3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive intermolecular hydrogen bonding in form II might be responsible.

scholarly journals Investigation of the Polymorphism of Osmium Tetrachloride

1969 ◽  
Vol 24 (2) ◽  
pp. 200-205 ◽  
Author(s):  
Paul Machmer
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependent ◽  
Orthorhombic Unit Cell ◽  
Magnetic Susceptibilities ◽  
X Ray ◽  
Space Groups ◽  
Temperature Form ◽  
High Temperature Form ◽  
First Ionization Potential

Depending on the method of preparation, osmium tetrachloride may be obtained in two different crystalline modifications, namely the high-temperature and the low-temperature forms. Both these species have been identified by elemental analysis and characterised by their respective x-ray powder photographs and magnetic susceptibilities. The x-ray powder data of the high-temperature form are tentatively rationalized in terms of an orthorhombic unit cell with the following dimensions: a = 12.08 A, b = 11.96 Å and c = 11.68 A. From the x-ray powder digram of the lowtemperature form the cubic lattice constant a = 9.95 Å is deduced. Reflection conditions for hkl and h00 are indicative of the space groups 06(P4332) and 07(P4132). Both compounds are paramagnetic and display low magnetic susceptibilities as a consequence of strong spin-orbit coupling. The high-temperature form exhibits the temperature-independent magnetic susceptibility χmole = +1080 × 10-6 c.g.s. units, whereas for the low-temperature form the value is χmole = +880 × 10-6 c.g.s. units (at 300°K). The latter susceptibility is temperature dependent. Some regularities between the uptake of chlorine by second- and third-row transition metals and the first ionization potential of the metals involved are discussed.

Low Temperature Synthesis of Porous Cordierite from Fly Ash

2006 ◽  
Vol 510-511 ◽  
pp. 638-641 ◽  
Author(s):  
Sung Jin Kim ◽  
Hee Gon Bang ◽  
Sang Yeup Park
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Low Temperature ◽  
Spinel Phase ◽  
Synthesis Temperature ◽  
Temperature Form ◽  
Metastable Form ◽  
Crystalline Forms ◽  
High Temperature Form ◽  
Porous Cordierite

Cordierite is known as three different crystalline forms, such as metastable form (µ- cordierite), high temperature form (α–cordierite; indialite), and low temperature form (β-cordierite). In general, cordierite has a phase transition behavior from metastable form to high temperature form. In this study, we focused to synthesize the porous cordierite at low temperature using reaction method without metastable form. When we used a pure starting powders (Al2O3, MgO, and SiO2), metastable cordierite and Mg spinel phase was obtained during the heat treatment. However, fly ash based mixture used as a starting powder, we obtained a porous α–cordierite at low synthesis temperature through transition from sapphirine/spinel and mullite/spinel

Structural Studies of GeTe-AgSbTe2 Alloys

2007 ◽  
Vol 1044 ◽  
Author(s):  
Alan Thompson ◽  
Jeff Sharp ◽  
C.J Rawn ◽  
B.C. Chackoumakos
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Systematic Study ◽  
Structural Studies ◽  
Temperature Form ◽  
P Type ◽  
High Temperature Form ◽  
Important Constituent

AbstractGeTe, a small bandgap semiconductor that has native p-type defects due to Ge vacancies, is an important constituent in the thermoelectric material known as “TAGS” [1]. TAGS is an acronym for alloys of GeTe with AgSbTe2, and compositions are normally designated as TAGS-x, where x is the fraction of GeTe. TAGS-85 is the most important with regard to applications, and there also is commercial interest in TAGS-80. The crystal structure of GeTe1+δ has a composition-dependent phase transformation at a temperature ranging from 430°C (δ = 0) to ∼ 400°C (δ = 0.02) [2]. The high temperature form is cubic. The low temperature form is rhombohedral for δ < 0.01, as is the case for good thermoelectric performance. Addition of AgSbTe2 shifts the phase transformation to lower temperatures, and one of the goals of this work is a systematic study of the dependence of transformation temperature on the parameter x. We present results on phase transformations and associated instabilities in TAGS compositions in the range of 70-85 at.% GeTe.

18-Krone-6 und kleine Carbonsäuren. Bildung und Struktur binärer Addukte mit Ameisen-und Essigsäure sowie ternärer mit Essigsäure und Wasser/18-Crown-6 and Small Carboxylic Acids. Formation and Structure of Binary Adducts with Formic and Acetic Acid, as well as Ternary Ones with Acetic Acid and Water

1998 ◽  
Vol 53 (2) ◽  
pp. 242-248 ◽  
Author(s):  
Antje Albert ◽  
Dietrich Mootz
Keyword(s):  
Hydrogen Bonding ◽  
Acetic Acid ◽  
High Temperature ◽  
Low Temperature ◽  
Binary Systems ◽  
Intermolecular Hydrogen Bonding ◽  
Temperature Form ◽  
Set Up ◽  
High Temperature Form ◽  
Ether Molecule

Abstract The melting diagrams of the binary systems 18-crown-6/formic acid and 18-crown-6/acetic acid have been set up and the crystal structures of the adducts 18C6 · 2 HCOOH (1, space group P 21/c with Z = 2 formula units per unit cell) and 18C6 · 2 CH3COOH (2, C2/m, Z = 2) determined. Furthermore three ternary phases, 18C6 · CH3COOH · H2O (3, P21/c, Z = 4) and dimorphic 18C6 · 2 CH3COOH · 4 H2O (high temperature form 4, P21/n, Z = 2; low temperature form 5, P21/n, Z = 2) have been characterized in the same way. In each structure the crown ether molecule has the (pseudo) D3d conformation common for many of its complexes. Various aspects of the intermolecular hydrogen bonding are described.

Two reversible enantiotropic phase transitions in a pentacoordinate silicon complex with anO,N,O′-tridentate valinate ligand

2015 ◽  
Vol 71 (6) ◽  
pp. 511-516 ◽  
Author(s):  
Anke Schwarzer ◽  
Sabine Fels ◽  
Uwe Böhme
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Low Temperature ◽  
Monoclinic Space Group ◽  
Isopropyl Group ◽  
Orthorhombic Space Group ◽  
Chiral Compound ◽  
Space Group ◽  
Temperature Form ◽  
High Temperature Form

Dimethyl[N-(4-oxidopent-3-en-2-ylidene)valinato-κ3O,N,O′]silicon(IV), C12H21NO3Si, (II), crystallizes in the orthorhombic space groupP212121. The chiral compound undergoes two sharp enantiotropic phase transitions upon cooling. The first transformation occurs at 163 K to yield a unit cell with one axis having double length. This intermediate-temperature form has the monoclinic space groupP21. The second transition takes place at 142 K and converts the single crystal into the low-temperature form in the orthorhombic space groupP212121. This transition proceeds under tripling of theaaxis of the high-temperature form. Both phase transitions are fully reversible and correspond to order–disorder transitions of the isopropyl group of the valine unit in the ligand backbone. The phase transitions presented here raise questions, since they do not fit into the rules of group–subgroup relationships.

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