Arthur Finch

Shrinkage of collagen fibres: A differential scanning calorimetric study

Abstract Differential scanning calorimetry has been used to study the thermal behaviour of bovine achilles tendon collagen, (a) in the solid state (13% water) (b) after swelling in deionised water. Shrinkage (denaturation) temperatures ( T D ) and denaturation enthalpies ( ΔH D ) were as follows: (a) T D = 112 ± 1 °C; ΔH D = 613 ± 39 cal·mole −1 (1 mole = 1 amino acid residue); (b) T D = 66 ± 1 °C; ΔH D = 803 ± 79 cal·mole −1 . The significance and relative magnitudes of these quantities are discussed and compared with relevant literature values. It is concluded that hydrophobic bonds are a major factor in the stabilisation of collagen fibres.

Differential scanning calorimetric study of collagen fibres swollen in aqueous neutral salt solutions.

The effect of various salts (KF, KCl, KCNS, CaF2, CaCl2 and Ca(CNS)2) at pH 5.6 to 6.2 on the enthalpy, ΔHD, and temperature, TD, of denaturation of swollen bovine achilles tendon collagen was studied. At dilute salt concentrations (< 0.3 M) marked differences in an estimated heat capacity function occur, from −40 to +30 cal · mole−1 · degree−1, although TD is decreased in all cases. At higher salt concentrations (0.3 to 2 M) the heat capacity function is of the same order of magnitude for all the salts studied (18–30 cal · mole−1 · degree−1) although TD is decreased with KCNS, CaCl2 and Ca(SCN)2 and increased with KF and KCl.

The thermal denaturation of collagen fibres swollen in aqueous solutions of urea, hexamethylenetetramine, p-benzoquinone and tetra-alkylammonium salts

Abstract The effect of urea, hexamethylenetetramine, p -benzoquinone, and tetra-alkylammonium salts on the enthalpy and temperature of denaturation of swollen collagen fibres was studied using differential scanning calorimetry. The results obtained suggest that hydrophobic interactions plays a significant role in stabilizing insoluble collagen, and may account for about 25% of the total stabilizing energy.

The vibrational spectra of diboron compounds—I. Infra-red spectra of diboron tetrafluoride

Abstract The infra-red spectrum of gaseous diborontetrafluoride has been measured from 4000 to 140 cm −1 . The point group and modal distribution for freely rotating B 2 F 4 have been deduced using nuclear permutation methods. Failure to see an absorption band of the expected frequency and intensity for an “out-of-plane” B BF 2 γ mode is shown to be consistent with free rotation or almost free rotation.

The vibrational spectra of compounds containing the dimethylamino grouping: Part I. Dimethylamine and tetrakis-dimethylamino diboron

Abstract The vibrational frequencies and approximate modes of dimethylamine have been computed using the technique of King and Crawford. It is shown that the band at 724 cm −1 is due to the symmetric—not the antisymmetric-NH deformation. The effect of increasing the mass of the amine hydrogen atom through the range 1 to 100 amu is explored and the results used to reinterpret the spectrum of tetra-kis dimethylamino diboron.

Single-halide anions in phosphorus(V) halide complexes: a raman investigation

Abstract Phosphorus(V) chloride and bromide complexes containing single-halide anions are surveyed in terms of characteristic phosphonium ion Raman shift patterns. Methods of preparation of Phase III phosphorus pentachloride are reviewed and some modes of formation proposed. The nature of the phosphonium cation-single-halide anion interaction is discussed on the basis of observed Raman shifts. With trihalide anions, similar shifts are observed but are strongly dependent on anion symmetry.

Thermochemistry of picrates. I. The standard enthalpy of formation of ammonium picrate

Abstract Using a static, oxygen-bomb calorimeter, the standard enthalpy of combustion at 298.15 K of the yellow crystalline modification of ammonium picrate has been determined as −2833.11 ± 2.83 kJ mole −1 . The standard enthalpy of formation is −385.44 ± 2.94 kJ mole −1 . These results are discussed in relation to previous values and also in connexion with solution calorimetric studies involving picric acid and metal picrates.

Enthalpy changes associated with the denaturation of collagens of different imino acid content

The enthalpy changes associated with the denaturation of acid-soluble and insoluble collagens prepared from sheep, cod, halibut and pike skin were determined by differential scanning calorimetry. The enthalpy change associated with the soluble collagens decreased with decreasing imino acid content (from 1420 cal/mol for sheep to 736 cal/mol for cod) while the value for insoluble collagens was approximately constant at 1360 cal/mol. A possible explanation for these values in terms of the nautre of the bonds present in collagen is discussed.

Thermodynamic functions for the congruent sublimation of cadmium telluride

Using a modified entrainment method the enthalpy and entropy changes for the reaction CdTe(c) ⇋ Cd(g)+0.5 Te2(g) at 298.15 K were determined as 72.0 ± 0.9 kcal mol-1 and 51.0 ± 0.8 cal K-1 mol-1, respectively, both values being significantly higher than previous estimates.

Thermochemistry of picrates. III. Enthalpies of solution and solubities of picrate salts

Abstract Using isoperibol solution-reaction calorimeters, the aqueous enthalpies of solution at 298.15 K of ammonium, caesium, potassium, silver, rubidium, tetramethylammonium and tetraethylammonium picrates have been determined as 45.81±0.35, 56.03±0.55, 51.14±0.55, 36.69±0.35, 55.01±0.36. 31.84±0.31 and 32.02±0.18 kJ mole −1 , respectively. Aqueous solubility data, as a function of temperature, have been measured for potassium, silver, ammonium, rubidium and caesium picrates by a precipitation method.