Optimality in self-organized molecular sorting

We introduce a simple physical picture to explain the process of molecular sorting, whereby specific proteins are concentrated and distilled into submicrometric lipid vesicles in eukaryotic cells. To this purpose, we formulate a model based on the coupling of spontaneous molecular aggregation with vesicle nucleation. Its implications are studied by means of a phenomenological theory describing the diffusion of molecules towards multiple sorting centers that grow due to molecule absorption and are extracted when they reach a sufficiently large size. The predictions of the theory are compared with numerical simulations of a lattice-gas realization of the model and with experimental observations. The efficiency of the distillation process is found to be optimal for intermediate aggregation rates, where the density of sorted molecules is minimal and the process obeys simple scaling laws. Quantitative measures of endocytic sorting performed in primary endothelial cells are compatible with the hypothesis that these optimal conditions are realized in living cells

Unearthing wave-function renormalization effects in the time evolution of a Bose-Einstein condensate

We study the time evolution of a Bose-Einstein condensate in an accelerated optical lattice. When the condensate has a narrow quasimomentum distribution and the optical lattice is shallow, the survival probability in the ground band exhibits a steplike structure. In this regime we establish a connection between the wave-function renormalization parameter $Z$ and the phenomenon of resonantly enhanced tunneling.Comment: 12 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1201.628

Analysis of ring laser gyroscopes including laser dynamics

Inertial sensors stimulate very large interest, not only for their application but also for fundamental physics tests. Ring laser gyros, which measure angular rotation rate, are certainly among the most sensitive inertial sensors, with excellent dynamic range and bandwidth. Large area ring laser gyros are routinely able to measure fractions of prad/s, with high duty cycle and bandwidth, providing fast, direct and local measurement of relevant geodetic and geophysical signals. Improvements of a factor $10-100$ would open the windows for general relativity tests, as the GINGER project, an Earth based experiment aiming at the Lense-Thirring test at $1\%$ level. However, it is well known that the dynamics of the laser induces non-linearities, and those effects are more evident in small scale instruments. Sensitivity and accuracy improvements are always worthwhile, and in general there is demand for high sensitivity environmental study and development of inertial platforms, where small scale transportable instruments should be used. We discuss a novel technique to analyse the data, aiming at studying and removing those non-linearity. The analysis is applied to the two ring laser prototypes GP2 and GINGERINO, and angular rotation rate evaluated with the new and standard methods are compared. The improvement is evident, it shows that the back-scatter problem of the ring laser gyros is negligible with a proper analysis of the data, improving the performances of large scale ring laser gyros, but also indicating that small scale instruments with sensitivity of nrad/s are feasible.Comment: 9 pages and 7 figure

UAV APPLICATION IN POST - SEISMIC ENVIRONMENT

Abstract. On April 6, 2009, an earthquake of 6.3 magnitude struck central Italy with its epicentre near L'Aquila, at 42.3502° N, 13.3762° E. The earthquake damaged 3000 to 11 000 buildings in the medieval city of L'Aquila. Several buildings totally collapsed, 308 people were killed. The post emergency phase till now is just at its beginning step. Conventional surveying techniques using high precision total stations, GNSS receivers and laser scanners for investigations on damaged buildings are always becoming more automated, accurate and operative and even much more fast. Even if these techniques represent instruments of extreme operability there are still many evident limits on their use, especially regarding the survey of both the roofs and the facades of tall buildings or dangerous places, typical on post earthquake situations. So using micro UAVs for surveying in such particular cases, many of these problems can be easily bypassed. In fact, the present work aims on experimenting using multi-rotor micro UAVs, that will allow high quality image capturing on roofs and facades of structures in the old city center of L'Aquila. To obtain actual stereoscopic acquisitions of buildings some conditions on the geometry of acquisition have to be observed, for this reason, taking as a guideline classic flight photogrammetric, a flight planning software was developed. Accurate planning for UAVs acquisitions is very important also considering the reduced autonomy of such vehicles. This can be a strategic point if we want to use UAVs for early damage assessment and also for post event reconstruction planning

Androgen receptor polymorphisms and testicular cancer risk

Testicular cancer (TC) is currently the most common malignant solid tumour in Caucasian males aged 15-39 years. Epidemiological evidence suggests that its onset may be due to an imbalance in the action of steroidal sex hormones and their receptors. A faulty androgen receptor signalling pathway can, in fact, cause various male reproductive disorders. The androgen receptor (AR) gene has two polymorphic segments consisting of CAG and GGC repeats. The length of CAG repeats has been shown to affect the regulation of AR activity. In our study, we used fragment analysis to evaluate the AR gene repeats of 302 TC patients and 322 controls, to establish if there is any association between repeat number and TC. This study of the largest Italian caseload investigated to date highlighted three particularly significant aspects. First, a CAG repeat number of ≥25 may be considered a risk factor for the onset of TC, given its greater frequency in patients in comparison with controls. This difference became significant for the non-seminoma group. Second, men with CAG repeats below 21 or above 24 were found to have a, respectively, 50 and 76% higher risk of TC than those with CAG 21-24, suggesting that these too can be considered a risk factor for TC. Finally, stage II patients were more likely to have a CAG repeat number 24 than stage I patients. © 2014 American Society of Andrology and European Academy of Andrology

Primary structure and tetrahydropteroylglutamate binding site of rabbit liver cytosolic 5,10-methenyltetrahydrofolate synthetase.

The primary sequence of 5,10-methenyltetrahydrofolate synthetase from rabbit liver was determined by amino acid sequencing of the purified enzyme. The enzyme contains 201 amino acid residues with a predicted mass of 22,779 Da. The enzyme is located in the cytosolic fraction of liver homogenates. Carbodiimide-activated 5-formyltetrahydropteroylmonoglutamate and the pentaglutamate form of the substrate both irreversibly inactivate the enzyme by forming a covalent bond to Lys-18. Non-activated 5-formyltetrahydropteroylpentaglutamate protected against this inactivation. Substrate specificity studies showed that increasing the number of glutamate residues from zero to five on 5-formyltetrahydropteroate results in a 2 order of magnitude increase in the affinity of the substrate for the enzyme but only a 3-fold increase in the value of Vmax

Inhibition of platelet aggregation by olive oil phenols via cAMP-phosphodiesterase

The aim of the present study was to confirm that olive oil phenols reduce human platelet aggregability and to verify the hypothesis that cAMP- and cGMP- phosphodiesterases (PDE) could be one of the targets of the biological effect. Four extracts from oils characterized by a high phenol content (HPE), and low phenol levels (LPE) were prepared and analyzed quali- and quantitatively by HPLC-UV and electrospray ionization–MS/MS. Human washed platelets stimulated with thrombin were used for the aggregation assay. Human platelet cAMP-PDE and recombinant PDE5A1 were used as enzyme source. Platelet aggregation and enzyme activity were assayed in the presence of HPE, LPE and individual phenols. The phenol content of HPE ranged between 250 and 500 mg/kg, whereas the LPE content was 46 mg/kg. The compounds identified were hydroxytyrosol (HT), tyrosol (TY), oleuropein aglycone (OleA) and the flavonoids quercetin (QU), luteolin (LU) and apigenin (AP). OleA was the most abundant phenol (range 23·3 to 37·7 %) and LU was the most abundant flavonoid in the extracts. Oil extracts inhibited platelet aggregation with an 50% inhibitory concentration interval of 1·23–11·2 μg/ml. The inhibitory effect of individual compounds (10 μm) including homovanillyl alcohol (HVA) followed this order: OleA>LU>HT = TY = QU = HVA, while AP was inactive. All the extracts inhibited cAMP-PDE, while no significant inhibition of PDE5A1 (50μg/ml) was observed. All the flavonoids and OleA inhibited cAMP-PDE, whereas HT, TY, HVA (100 μm) were inactive. Olive oil extracts and part of its phenolic constituents inhibit platelet aggregation; cAMP-PDE inhibition is one mechanism through which olive oil phenols inhibit platelet aggregation

The primary structure of rabbit liver mitochondrial serine hydroxymethyltransferase.

The complete amino acid sequence of mitochondrial serine hydroxymethyltransferase from rabbit liver was determined. The sequence was obtained from analysis of peptides isolated from chymotryptic, cyanogen bromide, and limited acid cleavages of the protein. The enzyme consists of four identical subunits, each of 475 residues, i.e. 8 residues shorter than the subunit of the corresponding cytosolic isoenzyme. The sequences of the two rabbit proteins are easily aligned, provided a gap of 5 residues near the amino terminus and a gap of 3 residues near the carboxyl terminus are included in the mitochondrial sequence. The overall degree of identity between the two isoenzymes is 61.9%, whereas the structural identity of each eukaryotic isoenzyme with the corresponding Escherichia coli enzyme is about 40%. The rabbit isoenzymes are about 70 residues longer than the E. coli enzyme, with one-half of these residues accounted for by insertions in both isoenzymes near their carboxyl terminus. Predictions of secondary structure and calculations of hydropathy profiles are also presented, suggesting an even more extensive degree of identity in the three-dimensional folding of the three proteins, in accord with the known similarity of their catalytic properties. Evidence was obtained for the existence of additional molecular forms of the mitochondrial protein, differing in the absence of some amino acid residues at the amino terminus of the polypeptide chain