NMR and X‐ray structural studies on 3‐benzyl‐8‐bromoadenine

8‐Bromoadenine was benzylated in the presence of base to give a mixture of two regioisomers. One was easily recognized as 9‐benzyl‐8‐bromoadenine, but the other structure could not be determined with absolute certainty by NMR. Therefore, X‐ray crystallography was used to prove that the benzyl group was attached to N‐3. Furthermore, it is shown that the 3‐benzyl adenine derivative exists as the amine tautomer both in the crystalline state as well as in solution (DMSO‐d₆), with restricted rotation around the N⁶? C6 bond. J. Heterocyclic Chem., (2011).     

Collective motion and nonequilibrium cluster formation in colonies of gliding bacteria

We characterize cell motion in experiments and show that the transition to collective motion in colonies of gliding bacterial cells confined to a monolayer appears through the organization of cells into larger moving clusters. Collective motion by nonequilibrium cluster formation is detected for a critical cell packing fraction around 17%. This transition is characterized by a scale-free power-law cluster-size distribution, with an exponent 0.88±0.07, and the appearance of giant number fluctuations. Our findings are in quantitative agreement with simulations of self-propelled rods. This suggests that the interplay of self-propulsion and the rod shape of bacteria is sufficient to induce collective motion.     

2‐Chloro‐6‐(2‐furyl)‐9‐(4‐methoxybenzyl)‐9H‐purine

The title compound, C₁₇H₁₃ClN₄O₂, displays profound and selective activity against Mycobacterium tuberculosis. In the crystal structure, there are two independent molecules in the asymmetric unit. Intermolecular hydrogen bonding between a CH group of the purine ring and the O atom of the furan ring, and also π–π stacking in another direction, builds the three‐dimensional network.     

Vortex Counting and Lagrangian 3-Manifolds

To every 3-manifold M one can associate a two-dimensional ${\mathcal{N}=(2, 2)}$ supersymmetric field theory by compactifying five-dimensional ${\mathcal{N}=2}$ super-Yang?CMills theory on M. This system naturally appears in the study of half-BPS surface operators in four-dimensional ${\mathcal{N}=2}$ gauge theories on one hand, and in the geometric approach to knot homologies, on the other. We study the relation between vortex counting in such two-dimensional ${\mathcal{N}=(2, 2)}$ supersymmetric field theories and the refined BPS invariants of the dual geometries. In certain cases, this counting can also be mapped to the computation of degenerate conformal blocks in two-dimensional CFT??s. Degenerate limits of vertex operators in CFT receive a simple interpretation via geometric transitions in BPS counting.     

A process analytical approach for quality control of dapivirine in HIV preventive vaginal rings by Raman spectroscopy

An estimated 34 million people are living with human immunodeficiency virus (HIV) worldwide. A polymeric drug delivery device for women has been developed to help reduce male to female vaginal transmission of HIV‐1. The device is an intravaginal slow‐release ring containing the antiretroviral drug dapivirine as the active pharmaceutical ingredient (API). In all pharmaceutical delivery systems, API content is a critical control point. Conventional quantification of the API in vaginal rings is a stepwise, destructive and time‐consuming process involving solvent extraction and high pressure liquid chromatography. This study investigates the potential of Raman spectroscopy for fast and non‐destructive quantification of dapivirine in intravaginal rings. Wide‐area illumination measurements were carried out on rotating rings using a custom built ring spinner. Customized reference rings of known concentrations were used to build calibration models, and the models were verified by rings from production using the established method as reference analysis. Bi‐ and multivariate calibration methods were applied. Models based on band ratios and partial least squares (PLS) regression models performed similarly well resulting in low model and prediction errors. Next to an alternative reference analysis for quality assurance, Raman can also be used as a production process performance analysis and optimization tool due to its non‐destructive nature and speed of analysis. Using measurements on connected spots over the entire ring circumference, the within ring variation in API was determined. ANOVA showed that there was a statistical difference in API distribution over the rings, information that can be of use in process optimization, for example. However, Tukey's honestly significant difference (HSD) test proved that no regions of the ring were out of specifications, indicating a stable production system. Copyright © 2014 John Wiley & Sons, Ltd.     

Vibrational deactivation of CO(v = 1) by p-H2. The importance of the higher-order multipole moments

Detailed calculations show that the agreement with the experimental rate constant for the vibrational deactivation of CO by p-H₂ is improved by including the octopole moment and the hexadecapole moment of CO. Previous calculations included only the dipole and the quadrupole moments. The present theoretical rates are 10–30 percent lower than the experimental values.     

Depth profiling of porcine adipose tissue by Raman spectroscopy

Raman spectroscopy was applied on a depth profile of porcine adipose tissue (from skin to meat) with the purpose of (1) discriminating between fat layers and (2) estimating the variation in fatty acid composition as a function of fat depth and fat layer: total degree of unsaturation (iodine value), fractions of saturated, and monounsaturated and polyunsaturated fatty acids. The thickness and composition of the outer layer of porcine adipose tissue influences the final quality of backfat. A too‐thick outer layer is associated with problems such as oily appearance, rancidity development, and difficulties in separating muscle and adipose tissue when cutting. From principal component analysis on standard normal variate preprocessed Raman spectra (1800–800 cm^–1), it was possible to discriminate between the outer and the inner backfat layer. Principal component analysis loadings showed that the separation of layer was mainly explained by variation in the bands originating from vibration of double bond C = C stretching plus = C–H twisting and rocking. In the prediction of iodine value a three‐component partial least squares regression model based on full range Raman spectra showed a root mean square error of cross validation of 2.00 and R² = 0.69. Applying Cauchy–Lorentz band fitting proved that information regarding fat unsaturation was found not only in band intensity, but also in band parameters such as location and width. The results suggest Raman spectroscopy as a potential measurement technique for rapid grading of pork carcasses. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and in-house validation of allergen-specific ELISA tests for the quantification of Dau c 1.01, Dau c 1.02 and Dau c 4 in carrot extracts (<Emphasis Type="Italic">Daucus carota</Emphasis>)

Even though carrot allergy is common in Europe, the amount of different allergens in carrots is still unknown due to a lack of methods for quantitative allergen measurements. The current study aimed at the development of quantitative ELISA tests for the known carrot allergens, namely Dau c 1.01, Dau c 1.02, and Dau c 4 in pure carrot extracts. Monoclonal antibodies targeting the major carrot allergen isoforms Dau c 1.01 and Dau c 1.02 were generated and combined in sandwich ELISA with rabbit antisera against Api g 1, the celery homologue of Dau c 1. A competitive ELISA for the carrot profilin Dau c 4 was based on a polyclonal rabbit antiserum. The three ELISA tests were allergen-specific and displayed detection limits between 0.4 and 6 ng allergen/ml of carrot extract. The mean coefficient of variation (CV) as a means of intraassay variability of the Dau c 1.01, Dau c 1.02 and Dau c 4 ELISA tests was 8.1%, 6.9%, and 11.9%, and the mean interassay CV 13.3%, 37.1% and 15.6%, respectively. Target recovery ranged between 93 and 113%. In conclusion, the specific, accurate and reproducible quantification of three important carrot allergens may help to identify less allergenic carrot varieties, as well as to standardize the amount of allergens in extracts used for carrot allergy diagnosis.