Carbon monoxide formation from trimethylamine-boranecarboxylate: DFT studies of SNi and chelotropic mechanisms

Trimethylamine-boranecarboxylic acid (CH₃)₃N-BH₂COOH and other amine carboxyboranes have been observed to undergo slow decarbonylation in neutral aqueous solution. This reaction, when it occurs in vivo, may have a therapeutic effect by delivering low concentrations of carbon monoxide over an extended period. In order to identify a possible mechanistic pathway for decarbonylation, the smallest tertiary amine derivative and its corresponding carboxylate ion were studied using CCSD(T)/PCM/6-311++G(2d,p)//M06-2X/PCM/6-311++G(2d,p) model chemistry. The proposed mechanistic pathway begins with a trimethylamine boranecarboxylate ion, which first undergoes an internal substitution reaction (S_Ni) to give free amine and the carboxyborane anion BH₂COO⁻. The latter cyclic ion then releases CO via a rapid chelotropic fragmentation. The role of water solvent in these reactions was explored by structural and energetic analysis of hydrogen-bonded complexes. It was found that complexation with water inhibits dissociation of trimethylamine by stabilizing the trimethylamine carboxyborane anion, whereas water accelerates CO loss by stabilizing the polar chelotropic transition state.

According to a DFT model, CO is formed from trimethylamine boranecarboxylate, a carbon monoxide releasing molecular pro-drug (CORM), via initial S_Ni subsitution followed by chelotropic fragmentation of the resulting cyclic carboxyborane anion.     

Acceptability of a Dapivirine/Placebo Gel Administered Rectally to HIV-1 Seronegative Adults (MTN-026)

AIDS and Behavior - This study describes the acceptability of a rectal microbicide gel formulation using dapivirine (DPV) among men and women from two countries (United States and Thailand)...     

A lyophilized formulation to extend the shelf-life of tuberculin PPD

This study was aimed to develop a dry purified protein devirative (PPD) preparation to extend the shelf-life of tuberculin PPD. Five percent sucrose (S), 6.5% mannitol (M), 2.5% trehalose (T) or 0.3% Hemaccel (H) was added to each formulation. In vivo and in vitro analyses were carried out to determine the efficacy of the lyophilized products. In the in vivo test, the delayed type hypersensitivity (DTH) responses of the lyophilized preparations were compared to the liquid preparation (CL) after injection into BCG vaccinated guinea pigs. The preparations of H, M, T, and S generated DTH responses of 100, 90, 89, and 60%, as compared to the response of CL, respectively. There was no loss of tuberculin activity in the H formula. A statistically significant difference in activity was found between S and CL (p < 0.05). The cellular test for IFN-gamma secretions was performed using the whole blood of human subjects screened for DTH response to tuberculin PPD Mantoux tests. The detection of IFN-gamma secretions was done using ELISA and the efficacy was expressed in terms of percentage of IFN-gamma responses to the tuberculin antigens. The results of CL, H, M, T and S were 3.28, 10.40, 0.84, 1.52 and 1.29%, compared to mitogen stimulation, respectively. The lyophilized H, M and T formulations and the liquid CL were studied for their shelf-life stabiliy. Accelerated degradation was done by storing the samples at higher temperatures of 37 degrees C and 56 degrees C for 3, 6, 9 and 12 months. All the tuberculin PPD solutions were injected into BCG vaccinated guinea pigs at the end of each storage period and the activity of each solution was evaluated. The formulation with the Hemaccel as excipient gave a superior response than the others at the normal storage temperature of 40 micro C for 12 months. Therefore, Hemaccel provides protection for PPD activity. This supports the potential for the development of lyophilized tuberculin PPD with the addition of 0.3% Hemaccel to extend shelf life.     

Detection of colorectal carcinoma by anti-CEA monoclonal antibody (IOR-CEA1) labeled with 99mTc scintigraphy

BACKGROUND/AIMS: This study shows that a new monoclonal antibody (IOR-CEA1) labeled with technetium-99m has high diagnostic efficacy for colorectal adenocarcinoma. This immunoscintigraphy is helpful in clinical management especially for patients whose serum carcinoembryonic antigen and computed tomography are questionable for recurrent diseases. The study aims to evaluate the efficiency of a new monoclonal antibody (IOR-CEA1) labeled with technetium-99m in the detection of colorectal carcinoma. METHODOLOGY: Forty colorectal carcinoma patients were examined. They were divided into 2 groups: Group I (9 patients) with untreated primary tumor; and Group II (31 patients) who were suspected of recurrent or residual diseases from 1) equivocal computed tomography or magnetic resonance imaging, or 2) rising serum carcinoembryonic antigen but normal imaging or clinical findings. One milligram of the antibody labeled with 25mCi of technetium-99m was slowly infused intravenously and images were obtained by nuclear medicine techniques. Sensitivity, specificity, accuracy, positive and negative predictive values were determined. RESULTS: 99mTc-IOR-CEA1 had 86% sensitivity, 71% specificity, 83% accuracy, 94% positive predictive value and 50% negative predictive value for the detection of colorectal cancer in 42 studies (2 patients had repeated studies). Serum carcinoembryonic antigen had only 33% sensitivity for detection of the primary cancer and 58% sensitivity in detection of recurrent diseases. Carcinoembryonic antigen had 100% positive predictive value but only 31.3% negative predictive value for diagnosis of the recurrence of tumor. Fifty-two percent of the antibody scans provided more information than computed tomography scans with clinical impact on further management in group II patients. CONCLUSIONS: The 99mTc-IOR-CEA1 scintigraphy is a promising investigative method which is safe and has high accuracy in the detection of recurrent colorectal carcinoma, especially in the patients whose serum carcinoembryonic antigen and computed tomography findings are equivocal for recurrent diseases.     

Pharmacokinetic studies of cyclosporine in Oriental kidney transplantation patients

SUMMARY: Pharmacokinetic studies were performed in 10 stable kidney transplantation patients who received microemulsion formulation (Neoral^®) of cyclosporine A (CsA) twice daily. No agents having pharmacokinetic effects on CsA had been used in these patients. The values of various basic pharmacokinetic parameters were similar to those reported in Western literature. The complete area under the blood concentration–time curve (AUC) of CsA for the duration of 12 h (12‐h AUC) was determined using the linear trapezoidal rule from seven concentrations at 0, 1, 2, 4, 6, 8, and 12 h after CsA administration. The mean values of 12‐h AUC were 4603.63 ± 344.61 ng h/mL. CsA concentrations at 2 h after dosing (not the trough levels) showed the best correlation with the complete AUC (r² = 0.9322). The abbreviated AUC of CsA was calculated either by stepwise multiple linear regression analysis or by the linear trapezoidal rule from a few sampling time points. Using stepwise multiple linear regression analysis, which was used in calculating abbreviated AUC in all previous studies, the model equation that had the highest correlation and the lowest prediction error with the complete AUC was derived by using CsA concentrations at 2 and 8 h after dosing (12‐h AUC = 4.262C₂ + 8.390C₈? 669.417; r² = 0.9808, absolute prediction error = 3.97 ± 0.96). Two model equations derived using the linear trapezoidal rule provided the best correlation with the complete AUC: (1) The two time points selected model equation 12‐h AUC = 4C₂ + 5C₈; r² = 0.9780, absolute prediction error = 6.41 ± 1.22). (2) The three time points selected model equation 12‐h AUC = 4C₀ + 3C₂ + 5C₆; r² = 0.9475, absolute prediction error = 5.00 ± 1.41). When different pharmacokinetic data sets were applied to the model equations derived using regression analysis, the values of coefficients and the constant of the regression equation had changed from the initial equation. Thus, new model equations will emerge every time the new data are applied. In contrast, the values of coefficients in the model equation calculated using trapezoidal rule were unaltered when tested by the new pharmacokinetic data set. Thus, the abbreviated AUC derived using the linear trapezoidal rule would be simpler than and superior to that obtained using stepwise multiple linear regression analysis in prediction of the complete AUC.     

Pharmacokinetics and placental transfer of single-dose tenofovir 1% vaginal gel in term pregnancy

Tenofovir (TFV) 1% vaginal gel has been found to decrease sexual transmission of human immunodeficiency virus. To initiate investigations during pregnancy, 16 healthy pregnant women scheduled for cesarean delivery received a single application of TFV gel preoperatively. Maternal serum drug concentrations were determined and fetal cord blood, amniotic fluid, placental tissue, and endometrial tissue specimens were collected. The median maternal peak concentration and cord blood TFV concentrations were 4.3 and 1.9 ng/mL, respectively (～100- and 40-fold lower than after TFV oral dosing, respectively). No adverse events were related to the use of TFV gel. These findings support ongoing and future investigations of TFV gel in pregnancy. CLINICAL TRIAL REGISTRATION: NCT00572273. http://www.clinicaltrials.gov/ct2/show/NCT00540605?term=mtn-002&rank=1.     

One-step purification of chimeric green fluorescent protein providing metal-binding avidity and protease recognition sequence

Gene fusion technique was successfully applied as a potential approach to create a metal-binding site to assist one-step purification of green fluorescent protein (GFP). The chimeric GFP carrying hexapolyhistidine (H6GFPuv) was purified to homogeneous protein via the Immobilized Metal Affinity Chromatography charged with zinc ions. Removal of metal tagger could readily be performed by using enterokinase enzyme. Engineering of the hexahistidine and enterokinase cleavage sites (DDDDK) onto the chimeric protein did not significantly affect the fluorescent property and the binding avidity to Burkholderia pseudomallei protease of a chimeric protease-binding GFP (H6PBGFPuv). This concludes that engineering of repetitive histidine regions onto interested target protein along with the enterokinase cleavage sites will ease the complication of protein purification.