Budding and vesiculation induced by conical membrane inclusions

Conical inclusions in a lipid bilayer generate an overall spontaneous curvature of the membrane that depends on concentration and geometry of the inclusions. Examples are integral and attached membrane proteins, viruses, and lipid domains. We propose an analytical model to study budding and vesiculation of the lipid bilayer membrane, which is based on the membrane bending energy and the translational entropy of the inclusions. If the inclusions are placed on a membrane with similar curvature radius, their repulsive membrane-mediated interaction is screened. Therefore, for high inclusion density the inclusions aggregate, induce bud formation, and finally vesiculation. Already with the bending energy alone our model allows the prediction of bud radii. However, in case the inclusions induce a single large vesicle to split into two smaller vesicles, bending energy alone predicts that the smaller vesicles have different sizes whereas the translational entropy favors the formation of equal-sized vesicles. Our results agree well with those of recent computer simulations.Comment: 11 pages, 12 figure

5.5-7.5 MeV Proton generation by a moderate intensity ultra-short laser interaction with H2O nano-wire targets

We report on the first generation of 5.5-7.5 MeV protons by a moderate intensity short-pulse laser (4.5 \times 1017 W/cm^2, 50 fsec) interacting with H2O nano-wires (snow) deposited on a Sapphire substrate. In this setup, the laser intensity is locally enhanced by the tip of the snow nano-wire, leading to high spatial gradients. Accordingly, the plasma near the tip is subject to enhanced ponderomotive potential, and confined charge separation is obtained. Electrostatic fields of extremely high intensities are produced over the short scale length, and protons are accelerated to MeV-level energies.Comment: submitted to PRL, under press embargo. 6 figure

DOC2B acts as a calcium switch and enhances vesicle fusion

Calcium-dependent exocytosis is regulated by a vast number of proteins. DOC2B is a synaptic protein that translocates to the plasma membrane (PM) after small elevations in intracellular calcium concentration. The aim of this study was to investigate the role of DOC2B in calcium-triggered exocytosis. Using biochemical and biophysical measurements, we demonstrate that the C2A domain of DOC2B interacts directly with the PM in a calcium-dependent manner. Using a combination of electrophysiological, morphological, and total internal reflection fluorescent measurements, we found that DOC2B acts as a priming factor and increases the number of fusion-competent vesicles. Comparing secretion during repeated stimulation between wild-type DOC2B and a mutated DOC2B that is constantly at the PM showed that DOC2B enhances catecholamine secretion also during repeated stimulation and that DOC2B has to translocate to the PM to exert its facilitating effect, suggesting that its activity is dependent on calcium. The hypothesis that DOC2B exerts its effect at the PMwas supported by the finding that DOC2B affects the fusion kinetics of single vesicles and interacts with the PM SNAREs (soluble NSF attachment receptors). We conclude that DOC2B is a calcium-dependent priming factor and its activity at the PM enables efficient expansion of the fusion pore, leading to increased catecholamine release. Copyright © 2008 Society for Neuroscience

Erythrocyte Phospholipid Molecular Species and Fatty Acids of Down Syndrome Children Compared with Non-affected Siblings

The majority of children with Down syndrome (DS) develop Alzheimer's disease (AD) at an early age. Although long-chain n-3 fatty acids (FA) are protective of neurodegeneration, little is known about the FA status in DS. In the present study, we aimed to investigate whether children with DS presented altered plasma and erythrocyte membrane phospholipids (PL) FA composition, when compared with their non-affected siblings. Venous blood samples were analysed for plasma and erythrocyte membrane FA composition by TLC followed by GC techniques. Lipid molecular species were determined by electrospray ionisation/tandem MS (ESI-MS/MS). FA analysis measured by standard GC showed an increased concentration of MUFA and a decreased concentration of plasmalogens in major PL fractions, but there were no differences in the concentrations of arachidonic acid or DHA. However, as identified by ESI-MS/MS, children with DS had increased levels of the following erythrocyte PL molecular species: 16 : 0–16 : 0, 16 : 0–18 : 1 and 16 : 0–18 : 2n-6, with reduced levels of 16 : 0–20 : 4n-6 species. Children with DS presented significantly higher levels of MUFA in both plasma and erythrocyte membrane, as well as higher levels of saturated and monounsaturated molecular species. Of interest was the almost double proportion of 16 : 0–18 : 2n-6 and nearly half the proportion of 16 : 0–20 : 4n-6 of choline phosphoacylglycerol species in children with DS compared with their non-affected siblings. These significant differences were only revealed by ESI-MS/MS and were not observed in the GC analysis. Further investigations are needed to explore molecular mechanisms and to test the association between the pathophysiology of DS and the risk of AD

Ubiquitin sets the timer: impacts on aging and longevity

Protein homeostasis is essential for cellular function, organismal growth and viability. Damaged and aggregated proteins are turned over by two major proteolytic routes of the cellular quality-control pathways: the ubiquitin-proteasome system and autophagy. For both these pathways, ubiquitination provides the recognition signal for substrate selection. This Commentary discusses how ubiquitin-dependent proteolytic pathways are coordinated with stress- and aging-induced signals

Pengaruh Gaya Kepemimpinan dan Karakteristik Individu Terhadap Pengembangan Karir Pada Lembaga Pemasyarakatan Kelas IIA Tanjung Raja

ABSTRAK Penelitian ini bertujukan guna mengetahui hubungan antara gaya kepemimpinan dengan sifat pribadi dan pertumbuhan karir di Lembaga Pemasyarakatan Tanjung Raja Kelas IIA. Dengan menerapkan metode total sampling dan metodologi kuantitatif, penelitian ini mencakup populasi sejumlah 83 karyawan, sehingga menghasilkan jumlah sampel secara keseluruhan sejumlah 83 karyawan. Pengumpulan data menerapkan kuesioner serta dokumentasi, dan pengujian koefisien korelasi, regresi linier sederhana, regresi linier berganda, pengujian asumsi klasik, dan penilaian koefisien determinasi diterapkan untuk analisis data. 1) Hasil uji t sejumlah 0,000 < 0,05 yang mencerminkan pengaruh gaya kepemimpinan terhadap kemajuan karir, menampakkan signifikansi temuan penelitian. 2) Hasil uji t sejumlah 0,000 < 0,05 menampakkan bahwasanya sifat individu juga bepengaruh pengaruh yang cukup besar terhadap kemajuan karir. Lebih lanjut, hasil uji F menampakkan bahwasanya di Lembaga Pemasyarakatan Kelas IIA Tanjung Raja atribut individu dan gaya kepemimpinan secara bersama-sama bepengaruh terhadap perkembangan karir. Pengaruh ini cukup besar, bertingkat signifikansi 0,000 < 0,05. Kata Kunci: Gaya Kepemimpinan, Karakteristik Individu dan Pengembangan Karir.   ABSTRACT This research aims to determine the relationship between leadership style and personal characteristics and career growth at the Class IIA Tanjung Raja Penitentiary. By using total sampling and quantitative methodology, this research covered a population of 83 employees, resulting in a total sample size of 83 employees. Data collection uses questionnaires and documentation, and correlation coefficient testing, simple linear regression, multiple linear regression, classical assumption testing, and assessment of the coefficient of determination are used for data analysis. 1) The t test results are 0.000 < 0.05 which reflects the influence of leadership style on career progress, indicating the significance of the research findings. 2) The t test results of 0.000 < 0.05 indicate that individual characteristics also have a fairly large influence on career progress. Furthermore, the results of the F test show that at the Class IIA Tanjung Raja Penitentiary, individual attributes and leadership style jointly influence career development. This effect is quite large, with a significance level of 0.000 <0.05. Keywords : Leadership Style,Individual Characteristics,Career Development

PENGEMBANGAN MODUL IPA BERBASIS PENDEKATAN SAINTIFIK MATERI SISTEM PERNAPASAN MANUSIA UNTUK KELAS V SD

Penelitian dan pengembangan ini bertujuan untuk menghasilkan sebuah produk berupa bahan ajar IPA berbasis pendekatan saintifik untuk kelas V Sekolah Dasar dengan judul “Modul IPA berbasis Pendekatan Saintifik Materi Sistem Pernapasan Kelas V Sekolah Dasar”. Penelitian ini menggunakan metode penelitian pengembangan dikenal juga Research and Development (R & D) yang mengacu pada model pengembangan Borg and Gall. Penelitian ini dilaksanakan di SDN Menteng Atas 02 Pagi Jakarta Selatan yang melibatkan siswa kelas V A sebanyak 26 peseta didik dan V B sebanyak 13 peserta didik. Penelitian ini menggunakan metode kuesioner, oservasi, dan wawancara. Penelitian dilaksanakan dalam empat tahap yaitu, uji ahli, evaluasi one to one, evaluasi small group, dan evaluasi field test. Hasil penilaian uji coba ahli media sebesar 100%, ahli materi sebesar 86%, dan ahli bahasa sebesar 95%. Hasil Penilaian evaluasi small group sebesar 95,5 % dan evaluasi field test sebesar 97,5%. Berdasarkan hasil penilaian secara keseluruhan Pengembangan Modul IPA Berbasis Pendekatan Saintifik masuk dalam kategori sangat baik