AH Values Research Articles

Carotenoid reaction with free radicals in acetone and toluene at different oxygen partial pressures

The influence of eight commonly occurring carotenoids on (1) the production of spin adducts, (2) the hyperfine splitting constants aH and aN of the spin adduct electron spin resonance (ESR) spectra, and (3) the production of the oxidized N-tert-butyl-α-phenylnitrone (PBN) derivative N-benzoyl-N-tert-butylnitroxide (PBNOx) was investigated in ESR spin-trapping experiments, in which radicals were thermally generated from 2,2′-azobis(2,4-dimethylvalero nitrile) (AMVN) and trapped by PBN. In the polar solvent acetone under air, all carotenoids except β-carotene were shown to diminish the number of spin adducts formed by about 20%. A prooxidative effect of β-carotene was even demonstrated at a higher concentration. In the less polar solvent toluene under air, most carotenoids lowered the amount of spin adducts, but effects were not as large as in acetone, and differences were found between (1) the more effective carotenoids with two cyclohexene rings conjugated to the polyene backbone (and lycopene), and (2) carotenoids with zero or one conjugated cyclohexene ring. The formation of PBNOx in toluene, which was essentially due to breakdown of peroxyl spin adducts, was significantly inhibited by astaxanthin, canthaxanthin and lycopene. Throughout, only alkoxyl radical adducts of PBN were observed. However, a significant difference was found between the aH values of zeaxanthin and the carbonyl carotenoid astaxanthin, indicating structural differences of the spin adducts.

Calorimetric techniques for studying drug-DNA interactions.

AbstractCalorimetric techniques can be used to measure the heat effects accompanying a drug-DNA interaction (1–3); in principle, one can calculate from these measurements both (4) the affinity (ΔG) and enthalpy change (ΔH) for the process. There are, however, many sites on the DNA lattice for interactions and assigning AH values for each IS dependent on the model used in the mathematical analysis. What can be obtained in most cases from careful calorimetric measurements is the AH for transferring a drug molecule from the aqueous environment to a site of high affinity on an unoccupied DNA lattice. Currently available calorimeters can be used at concentrations approaching levels used in UV-visible studies (1–5). Combination of the calorimetric measurements with an analysis of the corresponding binding isotherm can provide both the enthalpy and entropy changes (ΔG = ΔH - TΔS) for attaching a drug to a DNA lattice site (1–3,5).KeywordsPropidium IodideHeat EffectCalorimeter CellCommercial InstrumentCalorimetric TechniqueThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Dosimetry of mixed neutron and gamma radiation with paired Fricke solutions in light and heavy water.

Paired Fricke solutions, made up from light water or heavy water and 0.8N in H2SO4 and 1 mM in Fe(NH4)2(SO4)2 and NaCl, were calibrated with 60Co gamma rays and with mixed neutron and gamma radiation from a 252Cf source. Absorbance increases, AL and AH, in light- and heavy-water Fricke dosimeters, respectively, increased with fast-neutron and gamma-ray tissue doses, Dn (GY) and D gamma (GY), of the mixed radiation as follows: AL = 0.00178Dn + 0.00371D gamma; AH = 0.00121Dn + 0.00442 D gamma. G-values of 7.2 and 5.5 were obtained for 252Cf neutrons in light- and heavy-water Fricke dosimeters, respectively. When we applied the pair of equations to AL and AH values observed after exposure to mixed radiation in a nuclear reactor, resulting Dn and D gamma values agreed within 10% to doses measured with paired ionization chambers. Doses required for Fricke dosimeters were 5 Gy or more. In contrast, we found that micronuclear yields in onion roots can measure the neutron component of mixed radiation fields at the order of 10 cGy with reasonable accuracy even if the neutron to gamma-ray dose ratio is unknown.

A calorimetric study of ligand interactions with protons and metal ions in the 100 to 400 C range

Abstract

Thermodynamic and structural studies of cation-macrocycle interaction

Abstract

Thermodynamics of chemical interactions in aqueous solutions at elevated temperatures and pressures

Abstract

The NoH value in EPR spin trapping: a n ew parameter for the identification of 5,5-dimethyl-1-pyrroline-N-oxide spin adducts

The ratio of the nitrogen to hydrogen hyperfine splittings (aN/aH) of spin adducts derived from the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) has been found to be a useful parameter for adduct identification. For example, this parameter makes it possible to distinguish between the superoxide (aN/aH = 1.22-1.26) and peroxyl (aN/aH = 1.33-1.40) radical adducts of DMPO in aqueous solution. Since the aN to aH ratio corrects for minor differences in EPR spectrometer calibration, it is a more reproducible parameter than the aN and aH values themselves.

Bubble shapes in a liquid-filled rotating container under low gravity

The effect of surface tension on steady-state rotating fluids in a low-gravity environment is studied. AH values of the physical parameters used in the present calculations, except in the low-gravity environments, are based on the measurements carried out by Leslie in the low-gravity environment of a free-falling aircraft. The profile of the interface of two fluids is derived from Laplace's equation relating pressure drop across an interface to the radii of curvature that has been applied to a low-gravity rotating bubble that contacts the container boundary. The interface shape depends on the ratio of gravity to surface-tension forces, the ratio of centrifugal to surface tension forces, the contact radius of the interface to the boundary, and the contact angle. The shape of the bubble is symmetric about its equator in a zero-gravity environment. This symmetry disappears and gradually shifts to parabolic profiles as the gravity environment becomes nonzero. The location of the maximum radius of the bubble moves upward from the center of the depth toward the top boundary of the cylinder as gravity increases. The contact radius of interface to the boundary r0 at the top side of cylinder increases, and r0 at the bottom side of the cylinder decreases as the gravity environment increases from zero to 1 g.

Rate Theory and Polyethylene Relaxations

Polyethylene relaxation results are shown to be described very well by the rate theory associated with the name of Eyring. In agreement with this theory the oa, B, and ? relaxations have constant AH and AS values as long as the results are plotted properly, i. e. as log(?/T) vs 1/T. Since AS values are far from being negligible this means that the energy parameter typical of a given relaxation is the Gibbs free energy change ?G. It is shown that the ?G values of the ? relaxation are linearly related with crystallinity and not with crystallite thickness. In agreement with our theoretical model, the activation enthalpy and entropy of each relaxation are linearly related - the compensation law. It is concluded that important information on polymer relaxations can be gained from the ?S-?H plots.

Involvement of hydrogen-bonding protons in delocalization of the paramagnetic electron in a single crystal of photoreduced decatungstate

Diaquahydrogen tetrakis(di-isopropylammonium) decatungstate hexahydrate, [H5O2][NH2Pri2]4-[W10O32]·6H2O, has been studied in a single crystal, diamagnetically diluted by [H5O2]2-[NH2Pri2]4[W10O32]·4H2O in a ca. 1 : 1 molar ratio, by means of X-band e.s.r. spectroscopy at 77 K. The e.s.r. spectra show the superhyperfine interaction due to eight magnetically equivalent 1H atoms which are hydrogen-bonding water protons bonded to terminal oxygen atoms at eight equatorial WO6 sites. There is no observable 183W hyperfine interaction. The e.s.r. tensors are g1= 1.840 ± 0.001, g2= 1.838 ± 0.001, g3= 1.831 ± 0.001, AH1=(6.7 ± 0.1)× 10–4, AH2=(6.2 + 0.1)× 10–4, and AH3=(4.6 ± 0.1)× 10–4 cm–1, where each value is displaced from the tungsten–oxygen bond direction. The paramagnetic electron orbital involves the direct spin polarization of H (1s) orbitals and is delocalized over eight equatorial octahedra sites, through four nearly linear W–O–W bridges which link the two halves of the anion. The molecular g and AH values are discussed in terms of the molecular structure. It is concluded that the semioccupied molecular orbital consists of an orbital mixing among four sets of OW–O–WO multiple bonds which arrange the terminal WO groups cis to the nearly linear bridged moieties.

Glycosylated Hemoglobin and Plasma Protein in Newborns of Normal and Diabetic Women

The glycosylated hemoglobin (glyco Hb) and the glycoprotein of the plasma were determined using affinity chromatographic techniques in cord blood and maternal blood of normal (Group I), White's Class A diabetic (Group II), and insulin-dependent diabetic (Group III) mothers. The results revealed significant increase of glyco Hb (P less than 0.005) and glycoprotein (P less than 0.005) in the newborns of Group III mothers in comparison to those of Group I. The glyco Hb of maternal blood in this group also showed significant increase (P less than 0.005) while the increase in Hb A1 and plasma glycoprotein were nonsignificant. All values for cord blood and maternal blood of White's Class A diabetics revealed no significant change from the normal group. We conclude that the fetuses of insulin-dependent diabetic mothers are hyperglycemic in utero.

Enthalpy changes for intermediate steps of the ATP hydrolysis catalyzed by myosin subfragment-1.

The heat production during the ATP hydrolysis catalyzed by myosin subfragment 1 in 0.1 M KC1 containing 0.01 M MgClz and 0.02 M Tris/HCl (pH 7.8) at 23°C was followed using a microcalorimeter with an improved time resolution. The results indicate that: (a) the binding of ATP to Subfragment 1 is exothermic (AH = -90 kJ mol-‘, all the AH values are corrected for protonation heat of Tris). (b) The actual cleavage of ATP on Subfragment 1 is endothermic (AH = +83 kJ mol-I), which contrasts to the situation in free solution where ATP hydrolysis is exothermic, AH = -23 kJ mol-‘. Thus binding and cleavage together, which form the myosin+product complex at a rate which greatly exceeds the rate of decay of the complex (Pi release), is marginally exothermic (AH = -7 kJ mol-‘). (c) The slow Pi release is strongly exothermic (AH = -88 kJ mol-‘), as previously suggested by Yamada et al. (Yamada, T., Shimizu, H., and Suga, H. (1973) Biochim. Biophys. Acta 305, 643-653). (d) The dissociation of ADP from Subfragment 1 is endothermic (AH = +72 kJ mol-‘), being consistent with our recent result on the ADP binding to Subfragment 1 and heavy meromyosin (Kodama, T., Watson, I. D., and Woledge, R. C. (1977) J. Biol. Chem. 252,8085-8087). Thus in the myosin-catalyzed hydrolysis of ATP large enthalpy changes, as compared with the enthalpy change for the overall reaction, accompany several intermediate steps of the enzyme catalytic cycle. This is probably connected with the energy transduction role of myosin in muscle contraction.

A COMPONENT OF VARIANCE DUE TO COMPETITION1

Abstract and SummaryThe existence of a component of variance for competition among sampling units or among individuals in a group was discussed by Yates and Zacopany in 1935. No procedure was suggested for estimating this component of variance. It is the purpose of this paper to give a procedure for estimating the component of variance due to competition and to apply the procedure to a set of data on weaning weights of pigs with 116 litters of various sizes and for Yorkshire, Chester‐White, and Berkshire breeds. The first problem was to define litter size. Within this definition then, litters sizes of 3 to 14 pigs per litter were obtained. The variation among pigs within a litter of size h was considered to have an expected value equal to Vs+ Vch where Vs is the sampling variance component and Vch is the competition variance component for a litter of size h. In order to obtain an estimate of Vch, a polynomial relation between h and Vch was postulated. In particular, it was postulated that where E(.) denotes expected value. This form states that Vch goes to zero for one pig per litter; it may be appropriate as long as small litter sizes (say 1 and 2 at least) are omitted from the analysis as was done in the present instance.Using an iterative procedure of reestimating the weights at each stage, a form of weighted least squares analysis was performed. The procedure appears to converge after three to four steps of iteration. Solutions for some or all of the parameters Vp, Vs, β1 and β2 for h even, h odd, and all h = 3, 4, …, 14, were obtained using among litter mean squares, Ah, only, using within litter mean squares, Wh, only, and using both Ah, and Wh values. The Ah values for h = 3, 4, and 5 appeared to form a different group than for the other values of h. Both the Ah and Wh mean squares were from 56 day weights adjusted for birth weight.The maximum value of Vch for odd h, was nine whereas it was six for even h. Using all h the maximum value for Vch occurred when h was equal to nine. It appeared that expressing Vch as a quadratic function of litter size was satisfactory for these litter sizes and mean squares.

An ESR Study of N-Sulfonylaminyls

Abstract N-(3,5-Di-t-butylphenyl)-N-sulfonylaminyls, 3,5-t-Bu2C6H3–N–SO2-R, were investigated by means of ESR spectroscopy. The aN values are 7.8 G, and the aH values due to the N-phenyl ring protons are 5.6 (o-H) and 7.6 G (p-H). However, no couplings due to the protons in R have been detected. From these results, it is concluded that the unpaired electron is located on the nitrogen atom and the N-phenyl ring, negligibly delocalized onto the sulfonyl group.

Glass Transition Temperature of Polya-α-methylstyrene by Differential Scanning Calorimetry

Abstract Glass transition temperature (Tg) studies on poly-α-methylstyrene having M n values ranging from 2.9 × 103 to 7.0 × 104 were carried out with the DSC-2 differential scangng calorimeter. The variation of Tge (at q = l°K/min) with M n obeys the relation, Tge (°K) = 453–3.1 × 105 M n. The enthalpy change ΔH observed near the glass transition temperature drops to zero for zero annealing time and zero extrapolated heating rate conditions, suggesting that it is not necessary to postulate a first order transition to account for energy absorption. Operating with longer annealing periods or low heating rates yields similar trends as far as the AH values are concerned. Tg extrapolated to zero ΔH for zero extrapolated heat-ing rate conditions was found to increase with increasing annealing time.

Use of thermodynamic solubility parameters for the characterization of liquid phases

The differential enthalpy of evaporation from solution ( AH???) is reported the following functional groups: CH 2, OH, O , C O, CHO, OC(O)H, and OC(O)CH 3. These values are reported on seventy-five liquid phases using fifty solutes. The functional group AH values for the liquid phases have been used to rank the selectivity of the liquid phase towards each functional group.