Correlation of beta-bend conformations of tetrapeptides with their activities in CD4-receptor binding assays

Conformational analysis, based on ECEPP (Empirical Conformational Energy Program for Peptides) using the chain build-up procedure, was applied to determine the low-energy conformations for a series of tetrapeptides. The tetrapeptides are components of larger peptides which have been found to bind to the CD4 receptor of monocytes. Several previous studies have implicated the tetrapeptide units investigated here as being critical to the biological activities of the full peptides. Five such tetrapeptides were studied: Ser-Ser-Asn-Tyr (from ribonuclease A), Thr-Thr-Asn-Tyr (from peptide T, known to block human immunodeficiency virus from attaching to CD4+ T cells), Thr-Ile-Asn-Tyr (from polio virus coat protein, which is less active than the other peptides in binding to CD4 receptors), Ser-Ser-Ala-Tyr (from the gp 120 coat protein of human immunodeficiency virus, a variant of the peptide T sequence, active in blocking viral attachment to CD4+ cells), and the tetrapeptide from an active synthetic pentapeptide, Asn-Thr-Lys-Tyr (from Asn-Thr-Lys-Tyr-Thr). Using a 7 kcal/mol cutoff, the low-energy conformations for each peptide were computed. Approximately 20,000 conformations were computed for each tetrapeptide. Residue probability profiles were determined for each tetrapeptide. All tetrapeptides except for the polio sequence showed flexibility in the sense that many low-energy conformations were possible. In previous studies, it was postulated that the critical tetrapeptide units would adopt conformations similar to the one observed in a segment of ribonuclease A, residues 22-25, a beta-bend, which is part of an octapeptide segment (residues 19-26) that is homologous to the sequence of peptide T.(ABSTRACT TRUNCATED AT 250 WORDS)     

A Within-patient Comparison of Debrisoquine and Methyldopa in Hypertension

In a titrated dose cross-over trial of debrisoquine and methyldopa in 38 hypertensive patients neither drug was superior in lowering supine or standing diastolic pressure with a minimum of side effects. Methyldopa caused significantly greater reduction of supine (P<0·001) and standing (P<0·02) systolic pressure but caused intolerable side effects in two patients. Tiredness was the most characteristic and troublesome side effect with methyldopa and postural hypotension was prominent in patients while on debrisoquine.     

Correlation of structure with transforming activity of the P21 proteins with substitutions at positions 12 and 16

The structural effects of amino acid substitutions at positions 12 and 16 in the amino-terminal segment (Tyr 4-Ala 18) of the ras-oncogene-encoded P21 proteins have been investigated using conformational energy analysis. The P21 protein with Val at position 12 and Lys at position 16 is known to have high transforming ability, while the P21 protein with Val at position 12 and Asn at position 16 is known to have poor transforming ability, similar to that of the normal protein (with Gly at 12 and Lys at 16.) The current results demonstrate a significant conformational change at position 15 induced by the substitution of Asn for Lys at position 16, which could explain this alteration in transformation potential. These findings are consistent with previous results suggesting the existence of a normal and a malignancy-causing conformation for the P21 proteins and suggest that the critical transforming region may encompass residues 12–15.     

COMPARE analysis of the toxicity of an iminoquinone derivative of the imidazo[5,4-f]benzimidazoles with NAD(P)H:quinone oxidoreductase 1 (NQO1) activity and computational docking of quinones as NQO1 substrates

Synthesis and cytotoxicity of imidazo[5,4-f]benzimidazolequinones and iminoquinone derivatives is described, enabling structure-activity relationships to be obtained. The most promising compound (an iminoquinone derivative) has undergone National Cancer Institute (NCI) 60 cell line (single and five dose) screening, and using the NCI COMPARE program, has shown correlation to NQO1 activity and to other NQO1 substrates. Common structural features suggest that the iminoquinone moiety is significant with regard to NQO1 specificity. Computational docking into the active site of NQO1 was performed, and the first comprehensive mitomycin C (MMC)-NQO1 docking study is presented. Small distances for hydride reduction and high binding affinities are characteristic of MMC and of iminoquinones showing correlations with NQO1 via COMPARE analysis. Docking also indicated that the presence of a substituent capable of hydrogen bonding to the His194 residue is important in influencing the orientation of the substrate in the NQO1 active site, leading to more efficient reduction.     

Effect of a collaborative interdisciplinary maternity care program on perinatal outcomes

Background:

The number of physicians providing maternity care in Canada is decreasing, and the rate of cesarean delivery is increasing. We evaluated the effect on perinatal outcomes of an interdisciplinary program designed to promote physiologic birth and encourage active involvement of women and their families in maternity care.

Methods:

We conducted a retrospective cohort study involving 1238 women who attended the South Community Birth Program in Vancouver, Canada, from April 2004 to October 2010. The program offers comprehensive, collaborative, interdisciplinary care from family physicians, midwives, community health nurses and doulas to a multiethnic, low-income population. A comparison group, matched for neighbourhood of residence, maternal age, parity and gestational age at delivery, comprised 1238 women receiving standard care in community-based family physician, obstetrician and midwife practices. The primary outcome was the proportion of women who underwent cesarean delivery.

Results:

Compared with women receiving standard care, those in the birth program were more likely to be delivered by a midwife (41.9% v. 7.4%, p < 0.001) instead of an obstetrician (35.5% v. 69.6%, p < 0.001). The program participants were less likely than the matched controls to undergo cesarean delivery (relative risk [RR] 0.76, 95% confidence interval [CI] 0.68–0.84) and, among those with a previous cesarean delivery, more likely to plan a vaginal birth (RR 3.22, 95% CI 2.25–4.62). Length of stay in hospital was shorter in the program group for both the mothers (mean ± standard deviation 50.6 ± 47.1 v. 72.7 ± 66.7 h, p < 0.001) and the newborns (47.5 ± 92.6 v. 70.6 ± 126.7 h, p < 0.001). Women in the birth program were more likely than the matched controls to be breastfeeding exclusively at discharge (RR 2.10, 95% CI 1.85–2.39).

Interpretation:

Women attending a collaborative program of interdisciplinary maternity care were less likely to have a cesarean delivery, had shorter hospital stays on average and were more likely to breastfeed exclusively than women receiving standard care.In the last 2 decades, Canada has seen a dramatic reduction in the number of physicians providing maternity care.^1,2 Reasons for this decline have included liability concerns, lifestyle issues and perceived competence.³ A large proportion of obstetricians and family physicians who practise maternity care will reach retirement age in the next 10 years.⁴ The reduction in maternity care providers has been linked with hospital closures in rural settings and increasing difficulty in accessing obstetric care for women in all settings.⁴ Although the introduction of regulated midwifery promises some relief, midwives currently attend less than 10% of births.⁵Recent times have also seen a dramatic increase in the rates of interventions during childbirth, particularly cesarean delivery, which has risen from 17% in the 1990s to 28% in 2009 in Canada.⁶ This increase has occurred despite a lack of evidence that maternal and neonatal outcomes are improved with cesarean delivery.^7–10 Increasing rates of surgical delivery have placed an added burden on care provider resources, because of the associated intrapartum and postpartum complications¹¹ and increased length of stay in hospital.¹²In addition, increasing diversity, especially in urban settings, has made the delivery of maternity care more challenging. In the province of British Columbia, 16% of the population speaks neither official language at home.¹³ This proportion is as high as 32% in Vancouver, the province’s largest city and the setting of our study. There is evidence that immigrant women are at increased risk of receiving obstetric interventions and less likely to breastfeed.^14,15In response to these issues, the South Community Birth Program was established to provide comprehensive, collaborative maternity care from family physicians, midwives, community health nurses and doulas to a multiethnic, low-income population. The program aims to promote physiologic birth while encouraging women and their families to assume an active role in their maternity care. In the current study, we evaluated the impact of the program on perinatal outcomes.     

Structure-activity relationships of triazolopyridine oxazole p38 inhibitors: identification of candidates for clinical development

The synthesis, structure-activity relationship, in vivo activity, and metabolic profile for a series of triazolopyridine-oxazole based p38 inhibitors are described. The deficiencies of the lead structure in the series, CP-808844, were overcome by changes to the C4 aryl group and the triazole side-chain culminating in the identification of several potential clinical candidates.     

Ionizing radiation-dependent and independent phosphorylation of the 32-kDa subunit of replication protein A during mitosis

The human single-stranded DNA-binding protein, replication protein A (RPA), is regulated by the N-terminal phosphorylation of its 32-kDa subunit, RPA2. RPA2 is hyperphosphorylated in response to various DNA-damaging agents and also phosphorylated in a cell-cycle-dependent manner during S- and M-phase, primarily at two CDK consensus sites, S23 and S29. Here we generated two monoclonal phospho-specific antibodies directed against these CDK sites. These phospho-specific RPA2-(P)-S23 and RPA2-(P)-S29 antibodies recognized mitotically phosphorylated RPA2 with high specificity. In addition, the RPA2-(P)-S23 antibody recognized the S-phase-specific phosphorylation of RPA2, suggesting that during S-phase only S23 is phosphorylated, whereas during M-phase both CDK sites, S23 and S29, are phosphorylated. Immunofluorescence microscopy revealed that the mitotic phosphorylation of RPA2 starts at the onset of mitosis, and dephosphorylation occurs during late cytokinesis. In mitotic cells treated with ionizing radiation (IR), we observed a rapid hyperphosphorylation of RPA2 in addition to its mitotic phosphorylation at S23 and S29, associated with a significant change in the subcellular localization of RPA. Our data also indicate that the RPA2 hyperphosphorylation in response to IR is facilitated by the activity of both ATM and DNA-PK, and is associated with activation of the Chk2 pathway.     

Reducing bias through process inventory dataset normalization

Purpose  

This paper explores a computational method to resolve some of the problems of external normalization in the life cycle impact assessment (LCIA) process of midpoint characterized impacts. Problems inherent to external normalization (per capita per year for a defined region) that reduce the ability to accurately calculate the most significant impact categories include

Identification and partial characterization of an elastolytic protease in the amphibian pathogen Batrachochytrium dendrobatidis

Batrachochytrium dendrobatidis (Bd) is a fungus that causes chytridiomycosis, a disease that has been implicated as a cause of amphibian population declines worldwide. Infected animals experience hyperkeratosis and sloughing of the epidermis due to penetration of the keratinized tissues by the fungus. These symptoms have led us to postulate that Bd produces proteases that play a role in the infection process. Here, we show that Bd is capable of degrading elastin in vitro, a protein found in the extracellular matrix of the host animal. Elastolytic enzyme activity was partially purified using ion exchange chromatography and size-exclusion filtration from cultures grown in inducing media. The elastolytic activity of the purified fraction had a pH optimum of 8, was strongly inhibited by EDTA and phenylmethylsulfonyl fluoride (PMSF), and was partially inhibited by an elastase-specific inhibitor. This activity was also enhanced by the presence of Mg2+ and Ca2+ but not Zn2+. An antiserum directed against Aspergillus fumigatus serine protease (Alp) was found to react with a polypeptide of approximately 110 kDa from the purified material. Using immunofluorescence, this antiserum was also observed to react with zoospores and sporangia grown on toad skin. These observations suggest that Bd may produce proteases similar to those produced by other pathogenic fungi that are capable of degrading proteins found in the extracellular matrix. The proteolytic activity exhibited in vitro might aid the organism in its ability to colonize and destroy the epidermis of its amphibian host.