SNARE-mediated membrane fusion trajectories derived from force-clamp experiments.

Fusion of lipid bilayers is usually prevented by large energy barriers arising from removal of the hydration shell, formation of highly curved structures, and, eventually, fusion pore widening. Here, we measured the force-dependent lifetime of fusion intermediates using membrane-coated silica spheres attached to cantilevers of an atomic-force microscope. Analysis of time traces obtained from force-clamp experiments allowed us to unequivocally assign steps in deflection of the cantilever to membrane states during the SNARE-mediated fusion with solid-supported lipid bilayers. Force-dependent lifetime distributions of the various intermediate fusion states allowed us to propose the likelihood of different fusion pathways and to assess the main free energy barrier, which was found to be related to passing of the hydration barrier and splaying of lipids to eventually enter either the fully fused state or a long-lived hemifusion intermediate. The results were compared with SNARE mutants that arrest adjacent bilayers in the docked state and membranes in the absence of SNAREs but presence of PEG or calcium. Only with the WT SNARE construct was appreciable merging of both bilayers observed

Detector imperfections in photon-pair source characterization

We analyze how imperfections in single-photon detectors impact the characterization of photon-pair sources. We perform exact calculations to reveal the effects of multi-pair emissions and of noisy, non-unit efficiency, non photon-number resolving detections on the Cauchy-Schwarz parameter, on the second order auto-correlation and cross-correlation functions, and on the visibilities of both Hong-Ou-Mandel and Bell-like interferences. We consider sources producing either two-mode squeezed states or states with a Poissonian photon distribution. The proposed formulas are useful in practice to determine the impacts of multi-pair emissions and dark counts in standard tests used in quantum optics.Comment: 9 pages, 11 figure

Profiling of Glycan Receptors for Minute Virus of Mice in Permissive Cell Lines Towards Understanding the Mechanism of Cell Recognition

The recognition of sialic acids by two strains of minute virus of mice (MVM), MVMp (prototype) and MVMi (immunosuppressive), is an essential requirement for successful infection. To understand the potential for recognition of different modifications of sialic acid by MVM, three types of capsids, virus-like particles, wild type empty (no DNA) capsids, and DNA packaged virions, were screened on a sialylated glycan microarray (SGM). Both viruses demonstrated a preference for binding to 9-O-methylated sialic acid derivatives, while MVMp showed additional binding to 9-O-acetylated and 9-O-lactoylated sialic acid derivatives, indicating recognition differences. The glycans recognized contained a type-2 Galβ1-4GlcNAc motif (Neu5Acα2-3Galβ1-4GlcNAc or 3′SIA-LN) and were biantennary complex-type N-glycans with the exception of one. To correlate the recognition of the 3′SIA-LN glycan motif as well as the biantennary structures to their natural expression in cell lines permissive for MVMp, MVMi, or both strains, the N- and O-glycans, and polar glycolipids present in three cell lines used for in vitro studies, A9 fibroblasts, EL4 T lymphocytes, and the SV40 transformed NB324K cells, were analyzed by MALDI-TOF/TOF mass spectrometry. The cells showed an abundance of the sialylated glycan motifs recognized by the viruses in the SGM and previous glycan microarrays supporting their role in cellular recognition by MVM. Significantly, the NB324K showed fucosylation at the non-reducing end of their biantennary glycans, suggesting that recognition of these cells is possibly mediated by the Lewis X motif as in 3′SIA-LeX identified in a previous glycan microarray screen

Preventing Additive Attacks to Relational Database Watermarking

False ownership claims are carried on through additive and invertibility attacks and, as far as we know, current relational watermarking techniques are not always able to solve the ownership doubts raising from the latter attacks. In this paper, we focus on additive attacks. We extend a conventional image-based relational data watermarking scheme by creating a non-colluded backup of the data owner marks, the so-called secondary marks positions. The technique we propose is able to identify the data owner beyond any doubt

8-Methoxypsoralen Levels in Blood of Vitiligo Patients and in Skin, Ophthalmic Fluids, and Ocular Tissues of the Guinea Pig

8-Methoxypsoralen (8-MOP) levels in the blood of vitiligo patients were determined through the use of a reverse- phase high-performance liquid chromatographic method. The overall recovery of the internal standards was 85-94%, with the lower detection limit of 8-MOP at 2ng. Peak blood levels as low as 130ng/ml and as high as 3892 ng/ml were obtained in patients at 1-3h following the oral administration of 0.6mg/kg body weight of Oxsoralen capsules (Elder Pharmaceuticals Co.). These results are consistent with the clinical observation that maximum response in phototherapy is obtained at about 2h after oral administration of the drug. Two hours after oral administration of 0.6mg/kg of Oxsoralen, 8-MOP levels in the epidermis, dermis, and whole skin of the guinea pig (inng/g) were: epidermis, 330 ± 20; dermis, 89 ± 16; whole skin, 379 ± 19. Also detected were 8-MOP levels of 441 ± 22ng/ml in aqueous humor, 166 ± 18ng/ml in vitreous gel, 355 ± 15ng/g in lens, and 410 ± 26ng/g in retina. These results point to the fact that the eyes of the patient must be protected from exposure to sunlight after psoralen UV treatment, and that 8-MOP is absorbed in blood unevenly and varies from patient to patient. The fact that only 50-60% of the patients responded to psoralen photochemotherapy for vitiligo may be related to the variation of absorption of the drug in individual patients

“Without antibiotics, I cannot treat”: A qualitative study of antibiotic use in Paschim Bardhaman district of West Bengal, India

BACKGROUND:Misuse of antibiotics is a well-known driver of antibiotic resistance. Given the decentralized model of the Indian health system and the shortage of allopathic doctors in rural areas, a wide variety of healthcare providers cater to the needs of patients in urban and rural settings. This qualitative study explores the drivers of antibiotic use among formal and informal healthcare providers as well as patients accessing care at primary health centers across Paschim Bardhaman district in West Bengal. MATERIALS AND METHODS:We conducted 28 semi-structured, in-depth interviews with four groups of healthcare providers (allopathic doctors, informal health providers, nurses, and pharmacy shopkeepers) as well as patients accessing care at primary health centers and hospitals across Paschim Bardhaman district. Qualitative data was analyzed using the framework method in an inductive and deductive manner. RESULTS:Our results indicate that patients demand antibiotics from healthcare providers and seek the fastest cure possible, which influences the prescription choices of healthcare providers, particularly informal health providers. Many allopathic doctors provide antibiotics without any clinical indication due to inconsistent follow up, lack of testing facilities, risk of secondary infections, and unhygienic living conditions. Pharmaceutical company representatives actively network with informal health providers and formal healthcare providers alike, and regularly visit providers even in remote areas to market newer antibiotics. Allopathic doctors and informal health providers frequently blame the other party for being responsible for antibiotic resistance, and yet both display interdependence in referring patients to one another. CONCLUSIONS:A holistic approach to curbing antibiotic resistance in West Bengal and other parts of India should focus on strengthening the capacity of the existing public health system to deliver on its promises, improving patient education and counseling, and including informal providers and pharmaceutical company representatives in community-level antibiotic stewardship efforts

Does Greater Low Frequency EEG Activity in Normal Immaturity and in Children with Epilepsy Arise in the Same Neuronal Network?

Greater low frequency power (<8Hz) in the electroencephalogram (EEG) at rest is normal in the immature developing brain of children when compared to adults. Children with epilepsy also have greater low frequency interictal resting EEG activity. Whether these power elevations reflect brain immaturity due to a developmental lag or the underlying epileptic pathophysiology is unclear. The present study addresses this question by analyzing spectral EEG topographies and sources for normally developing children and children with epilepsy. We first compared the resting EEG of healthy children to that of healthy adults to isolate effects related to normal brain immaturity. Next, we compared the EEG from 10 children with generalized cryptogenic epilepsy to the EEG of 24 healthy children to isolate effects related to epilepsy. Spectral analysis revealed that global low (delta: 1-3Hz, theta: 4-7Hz), medium (alpha: 8-12Hz) and high (beta: 13-25Hz) frequency EEG activity was greater in children without epilepsy compared to adults, and even further elevated for children with epilepsy. Topographical and tomographic EEG analyses showed that normal immaturity corresponded to greater delta and theta activity at fronto-central scalp and brain regions, respectively. In contrast, the epilepsy-related activity elevations were predominantly in the alpha band at parieto-occipital electrodes and brain regions, respectively. We conclude that lower frequency activity can be a sign of normal brain immaturity or brain pathology depending on the specific topography and frequency of the oscillating neuronal networ