The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc-AcOH buffer in the pH range 3.73-4.77. The reaction is first order with respect to both Au(III) and glycine. Both H + and Cl -ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium. AuCl 4 -and AuCl 3 (OH) -are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product by 1 H NMR spectroscopy.

The effect of an ionic (SDS) and two nonionic (TX-100 and Tween 20) surfactants on the electron transfer reaction between L-leucine and gold(III) complexes has been investigated in acetate buffer. H + , Cl − , and decreasing dielectric constant of the medium have inhibiting effects on the reaction rate. The reaction product has been identified as isovaleraldehyde by 1 H NMR. Two different Au(III) species and the zwitterion form of the amino acid react where Au(III) undergoes a one step two-electron transfer process. In the presence of surfactants, the postmicellar kinetics has been explained in the light of Berezin's model where both the oxidant and the substrate are solubilized in the micellar pseudophase and then react. The leucine molecules occupy the hydrophobic core of the micelle with the polar amino and acid groups projected in the Stern/palisade layer among the surfactant head-groups and the oxidant species. The binding constants for substrate−micelle association and the corresponding enthalpy changes have been evaluated. The hydrophobic interaction of leucine with SDS micelles is greater than those with Tween 20 and TX-100 micelles. The compensation between substrate−water interaction and substrate−micelle interaction determines the enthalpy change for the substrate−micelle association. Entropy change for (Leu) W → (Leu) M controls substrate−micelle binding.

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by 1 H NMR spectroscopy. Under the experimental conditions, AuCl − 4 and AuCl 3 (OH) − are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H + and Cl − on the secondorder rate constant k 2 have been analyzed, and accordingly the rate law has been deduced:. Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed.

The effect of nonionic micelles of Triton X-100 on the oxidative decarboxylation of L-glutamic acid by chloroaurate(III) complexes has been investigated in acetate buffer medium. The reaction is first order with respect to Au(III), but a complex order with respect to glutamate. H + ion has both accelerating and retarding effects in the pH range 3.72-4.80, whereas a Cl − ion has an inhibiting effect in the range 0.02-0.56 mol dm −3 . Under the experimental conditions, AuCl − 4 and AuCl 3 (OH) − are the predominant and effective oxidizing species, whereas the zwitterion (H 2 A) and mononegative anion (HA − ) are the predominant reducing species of the amino acid. The reaction involves a one-step two-electron transfer process and passes through the intermediate formation of iminic cation. In the presence of surfactant, the reaction passes through a maximum and it appears to follow Berezin's model, where both the oxidant and the substrate are partitioned between the aqueous and the micellar phase and then react. The binding constants between the reactants and the surfactant have been evaluated at different temperatures. Compensation between substrate-water interaction and substrate-micelle interaction plays an important role in such redox reactions in the presence of a surfactant.

Background: Ovarian tumours are common problem in gynaecology and have varied age of appearance of different histopathological types. Objective: This study was undertaken to find out the relationship of age and different histological types of ovarian tumors Methods: A retrospective study was carried out in the Department of Obstetrics and Gynaecology and Department of Pathology, Sir Salimullah Medical College and Mitford Hospital, Dhaka, during May 2010 and December 2014. Five hundred forty seven (547) cases of ovarian tumours were studied in respect to their age and histopathological appearance. Results: The range of age of patients with ovarian tumour was 11 – 82 years. About 63% malignant and 73% benign ovarian tumours were found in the age group of 20 – 49 yrs. About 31% malignant ovarian tumours and 15% Benign tumours occurred in menopausal woman (≤50 yrs.). Overall, mean age of presentation of ovarian tumours was 34.29± 12.84 yrs. Mean age of patients with malignant ovarian tumour was 40.29± 14.28 (median 40 yrs; mode 45 yrs.). Mean age of benign ovarian tumour was 34.69 ± 13.08 (median 34 yrs; mode 40yrs) and mean age for borderline tumours 32.75 ± 11.70 mm (median 33 yrs., mode 20 yrs.). Mean age of non tumour ovarian masses / cysts was 31.14± 10.76 yrs (median 29.5; mode 25.4). The difference of mean age of occurance of malignant and benign ovarian tumours were statistically significant P<0.00>. Dysgerminoma (mean age 23.5± 4.43) and yolk sac tumour (mean age 18 .00 ± 5.00 yrs) occurred in younger patients. Serous cyst adenocarcinoma, endometriod carcinoma and poorly differentiated carcinoma occurred around 45 years of age. Mean age of presentation of most of the benign ovarian tumours was between 30 – 37 yrs.; except thecoma which occurred in extremes of age. Conclusion: Most of the patients with malignant and benign ovarian tumours have presented in reproductive age adult women (20 – 49 yrs.); and some specific varieties of tumour (e.g. thecoma) presented in the extremes of age. Bangladesh J Obstet Gynaecol, 2017; Vol. 32(2) : 99-105