Synthetic Applications of Flexible SNO-OCT Strained Alkynes and Their Use in Postpolymerization Modifications.

SNO-OCTs are eight-membered heterocyclic alkynes that have fast rates of reactivity with 1,3-dipoles. In contrast to many other reported cycloalkynes, SNO-OCTs contain multiple sites for derivatization, display stability under a variety of common reaction conditions, and offer the opportunity for strain-induced ring-opening following the initial reaction of the alkyne moiety. In this paper, we describe how the unique features of SNO-OCTs can be employed to modify an oxime-bearing styrene copolymer and introduce an array of polar functionalities into the polymer. This can be achieved through both the addition of SNO-OCT to the polymer, as well as in the subsequent opening of the sulfamate ring once it has been installed in the polymer.

Fine-Tuning Strain and Electronic Activation of Strain-Promoted 1,3-Dipolar Cycloadditions with Endocyclic Sulfamates in SNO-OCTs.

The ability to achieve predictable control over the polarization of strained cycloalkynes can influence their behavior in subsequent reactions, providing opportunities to increase both rate and chemoselectivity. A series of new heterocyclic strained cyclooctynes containing a sulfamate backbone (SNO-OCTs) were prepared under mild conditions by employing ring expansions of silylated methyleneaziridines. SNO-OCT derivative 8 outpaced even a difluorinated cyclooctyne in a 1,3-dipolar cycloaddition with benzylazide. The various orbital interactions of the propargylic and homopropargylic heteroatoms in SNO-OCT were explored both experimentally and computationally. The inclusion of these heteroatoms had a positive impact on stability and reactivity, where electronic effects could be utilized to relieve ring strain. The choice of the heteroatom combinations in various SNO-OCTs significantly affected the alkyne geometries, thus illustrating a new strategy for modulating strain via remote substituents. Additionally, this unique heteroatom activation was capable of accelerating the rate of reaction of SNO-OCT with diazoacetamide over azidoacetamide, opening the possibility of further method development in the context of chemoselective, bioorthogonal labeling.

Oxidative allene amination for the synthesis of azetidin-3-ones.

Regioselectivity in the aziridination of silyl-substituted homoallenic sulfamates is readily diverted to the distal double bond of the allene to yield endocyclic bicyclic methyleneaziridines with excellent stereocontrol. Subsequent reaction with electrophilic oxygen sources initiates facile rearrangement to densely functionalized, fused azetidin-3-ones in excellent d.r., effectively transferring the axial chirality of the allene to central chirality in the products. The steric nature of the silyl group dictates which of the two rings of the fused azetidin-3-one will undergo further functionalization, providing an additional element of diversity for the preparation of enantioenriched azetidine scaffolds with potential biological activity.

Ternary nylon-3 copolymers as host-defense peptide mimics: beyond hydrophobic and cationic subunits.

Host-defense peptides (HDPs) are produced by eukaryotes to defend against bacterial infection, and diverse synthetic polymers have recently been explored as mimics of these natural peptides. HDPs are rich in both hydrophobic and cationic amino acid residues, and most HDP-mimetic polymers have therefore contained binary combinations of hydrophobic and cationic subunits. However, HDP-mimetic polymers rarely duplicate the hydrophobic surface and cationic charge density found among HDPs ( Hu , K. ; et al. Macromolecules 2013 , 46 , 1908 ); the charge and hydrophobicity are generally higher among the polymers. Statistical analysis of HDP sequences ( Wang , G. ; et al. Nucleic Acids Res. 2009 , 37 , D933 ) has revealed that serine (polar but uncharged) is a very common HDP constituent and that glycine is more prevalent among HDPs than among proteins in general. These observations prompted us to prepare and evaluate ternary nylon-3 copolymers that contain a modestly polar but uncharged subunit, either serine-like or glycine-like, along with a hydrophobic subunit and a cationic subunit. Starting from binary hydrophobic-cationic copolymers that were previously shown to be highly active against bacteria but also highly hemolytic, we found that replacing a small proportion of the hydrophobic subunit with either of the polar, uncharged subunits can diminish the hemolytic activity with minimal impact on the antibacterial activity. These results indicate that the incorporation of polar, uncharged subunits may be generally useful for optimizing the biological activity profiles of antimicrobial polymers. In the context of HDP evolution, our findings suggest that there is a selective advantage to retaining polar, uncharged residues in natural antimicrobial peptides.

Field evaluation of diagnostic accuracy of an oral fluid rapid test for HIV, tested at point-of-service sites in rural Zimbabwe.

The objective of this study was to validate the use of OraQuick ADVANCE Rapid HIV-1/2 Antibody test (OraSure Technologies Inc., Bethlehem, PA) on oral fluid for a population-based HIV prevalence survey of rural youth in southeast Zimbabwe. The evaluation was conducted in patients presenting for voluntary counseling and testing at rural clinics. Each participant provided an oral fluid sample tested using OraQuick ADVANCE. In addition, dried blood specimens were collected and tested blind at the National Microbiology Reference Laboratory in Harare using two enzyme-linked immunosorbent assays (ELISA; Vironostika, Biomérieux BV, Boxtel, The Netherlands and Ani Labsystems, Ltd., Vantaa, Finland) with confirmatory Western blot (MP Diagnostics [formerly Genelabs Diagnostics], Medical Technology Promedt Consulting GMBH, St. Ingbert, Germany) for samples with discrepant results. Diagnostic accuracy of the oral fluid assay was determined against the ELISA/Western blot algorithm as gold standard. Five hundred and ninety-one participants took part in the study between February and July 2006. Sensitivity of the test on oral fluid was 100% (95% confidence interval [CI]: 97.9-100), and specificity was 100% (95% CI: 99.1-100). HIV prevalence based on the reference standard was 29.8% (95% CI: 26.1-33.5). This is one of the first validations of this rapid assay on oral fluid conducted in a general population to be reported in Africa. While there are some limitations with the assay (e.g., unlikely to detect those in early stages of HIV infection or with reduced viral load; altered accuracy in pregnancy) these limitations also apply to other rapid assays. The results showed the assay to be 100% accurate in determining HIV status, performed well in field settings, and can be considered suitable for use in epidemiologic surveys aiming to estimate HIV prevalence in general populations.

Evaluation of the Partec flow cytometer against the BD FACSCalibur system for monitoring immune responses of human immunodeficiency virus-infected patients in Zimbabwe.

A single-platform volumetric flow cytometer, the Partec Cyflow SL_3, was evaluated against a BD FACSCalibur/Sysmex XT1800i dual platform for measuring CD4(+) lymphocytes, total lymphocytes, and the percentage of CD4 lymphocytes in whole-blood samples for monitoring the immune systems of human immunodeficiency virus (HIV)/AIDS patients. Statistical analyses for precision, correlation, and agreement were performed. Coefficients of variation (CV) of 5.8, 4.6, and 3.9% were obtained for low, medium, and high CD4(+) cell counts, respectively, using the SL_3, and CV of 3.7, 4.0, and 0.94 were obtained for the same categories, using the BD FACSCalibur. Significant correlations (P < 0.005) between the two assays for CD4 counts, total lymphocyte counts, and percentages of CD4 were obtained, with correlation coefficients of 0.99, 0.96, and 0.99, respectively (n = 229). Using the Bland-Altman plot, mean biases of -18 cell/microl (95% confidence interval (CI); -91 to 54 cells/microl), -0.8% (95% CI; -3.6 to 2%), and -36.8 cells/microl (95% CI; -477 to 404 cells/microl) were obtained for comparisons of CD4 counts, percentages of CD4 cells, and total lymphocyte counts, respectively. The effects of the age of the samples on the three parameters were also analyzed by comparing results from the same samples analyzed at 6, 24, and 48 h after collection. The correlation coefficients for comparisons among different time points for the same machine and among all the time points for the two different machines were greater than 0.90. These data showed that the Partec Cyflow SL_3 assay is comparable to the BD FACSCalibur/Sysmex XT1800i dual-platform method for measuring the amount of CD4(+) cells and total lymphocytes and the percentages of CD4 cells in blood samples for the purpose of monitoring HIV/AIDS patients.