First-Passage Time Distribution and Non-Markovian Diffusion Dynamics of Protein Folding

We study the kinetics of protein folding via statistical energy landscape theory. We concentrate on the local-connectivity case, where the configurational changes can only occur among neighboring states, with the folding progress described in terms of an order parameter given by the fraction of native conformations. The non-Markovian diffusion dynamics is analyzed in detail and an expression for the mean first-passage time (MFPT) from non-native unfolded states to native folded state is obtained. It was found that the MFPT has a V-shaped dependence on the temperature. We also find that the MFPT is shortened as one increases the gap between the energy of the native and average non-native folded states relative to the fluctuations of the energy landscape. The second- and higher-order moments are studied to infer the first-passage time (FPT) distribution. At high temperature, the distribution becomes close to a Poisson distribution, while at low temperatures the distribution becomes a L\'evy-like distribution with power-law tails, indicating a non-self-averaging intermittent behavior of folding dynamics. We note the likely relevance of this result to single-molecule dynamics experiments, where a power law (L\'evy) distribution of the relaxation time of the underlined protein energy landscape is observed.Comment: 26 pages, 10 figure

Diffusion Dynamics, Moments, and Distribution of First Passage Time on the Protein-Folding Energy Landscape, with Applications to Single Molecules

We study the dynamics of protein folding via statistical energy-landscape theory. In particular, we concentrate on the local-connectivity case with the folding progress described by the fraction of native conformations. We obtain information for the first passage-time (FPT) distribution and its moments. The results show a dynamic transition temperature below which the FPT distribution develops a power-law tail, a signature of the intermittency phenomena of the folding dynamics. We also discuss the possible application of the results to single-molecule dynamics experiments

Regularization dependence of pion generalised parton distributions

Pion generalised parton distributions are calculated within the framework of the Nambu--Jona-Lasinio model using different regularization schemes, including the proper time regularization scheme, the three dimensional momentum cutoff scheme, the four dimensional momentum cutoff scheme, and the Pauli-Villars regularization scheme. Furthermore, we check the theoretical constraints of pion generalised parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes. The diagrams of pion parton distribution functions are plotted, in addition, we evaluate the Mellin moments of generalised parton distributions, which related to the electromagnetic and gravitational form factors of pion. Pion generalised parton distributions are continuous but not differential at $x=\pm \,\xi$, when considering the effect of D-term, generalised parton distributions become not continuous at $x=\pm \,\xi$ in all the four regularization schemes. Generalised parton distributions in impact parameter space are considered, the width distribution of $u$ quark in the pion and the mean-squared $\langle \mathbf{b}_{\bot}^2\rangle_{\pi}^u$ are calculated. The light-front transverse-spin distributions are studied, when quark polarized in the light-front-transverse $+\,x$ direction, the transverse-spin density is no longer symmetric around $(b_x=0,b_y=0)$, the peaks shift to $(b_x=0,b_y>0)$, we compare the average transverse shift $\langle b_{\bot}^y\rangle_1^u$ and $\langle b_{\bot}^y\rangle_2^u$ in different regularization schemes. The light-cone energy radius $r_{E,LC}$ and the light-cone charge radius $r_{c,LC}$ are also evaluated, we find that in the proper time regularization scheme the values of these quantities are the largest, in the three dimensional momentum cutoff scheme they are the smallest.Comment: 34 pages, 39 figure

A meta-analysis of Pemetrexed plus Platinum Chemotherapy versus Gemcitabine plus Platinum Chemotherapy for Advanced Non-small Cell Lung Cancer

Background and objective Whether pemetrexed plus platinum (PP) regimen is superior to gemcitabine plus platinum (GP) regimen for patients with advanced non-small cell lung cancer (NSCLC) is unclear. The aim of this study is to evaluate the efficacy and safety of PP versus GP regimens for patients with NSCLC. Methods We searched relevant randomized controlled trials (RCTs) from Pubmed, EMBASE, Cochrane Library, Chinese Journal Full-text Database, Chinese Biomedical Literature Database, Chinese Scientific Journals Full-text Database, and traced the related references to obtain the information that has not been found. We made quality assessment of qualified RCTs assessed by the exclusion and inclusion criteria and used RevMan 5.0 provided by the Cochrane Collaboration to perform meta-analysis. Results Four RCTs involving 2,235 patients were identified. There were no statistical differences between PP and GP regimens in one-year survival rate (OR=1.09, 95%CI: 0.91-1.29), the efficiency of disease (OR=1.00, 95%CI: 0.40-2.52), but overall survival (MD=0.26, 95%CI: 0.21-0.30), alopecia (OR=0.51, 95%CI: 0.39-0.66) and hematologic toxicity were significantly different. Conclusion The clinical efficiency of PP and GP regimens for advanced NSCLC was similar, but the side effects were different. The toxicity of PP regimen has the tendency to be more tolerable

Clinical analysis of high myopia in 320 cases in Ningxia Hui Autonomous Region

AIM: To analyze the clinical manifestations and etiological factors of high myopia in 320 cases. <p>METHODS:A total of 320 patients(640 eyes)with high myopia treated in Ningxia Eye Hospital from January 2011 to November 2012 were studied. All of them underwent thorough eye examination and relevant environmental factors were recorded. The following data were analyzed, including gender, ethnicity, age of onset, refractive error, axial length, best corrected visual acuity(BCVA), educational level and living environment. <p>RESULTS: Bilateral high myopia was present in 320 patients(130 men and 190 women; 250 being of Han nationality and 70 of Hui nationality)with a mean age of 42.65±16.51 years(range: 3-80 years); the male to female ratio was 1:1.5. The age of onset was lower than 20 years in 237 patients, higher than 21 yeas in 83 patients, the difference was statistically significant(<i>P</i><0.001). There was no significant difference between diopter and educational level(<i>P</i>>0.05). The patients with BCVA higher than 0.3 increased with diopter increased, while BCVA lower than 0.8 and between 0.4～0.7 reduced. Refraction was significantly negatively correlated with BCVA(<i>r</i>=-0.196, <i>P</i><0.05)and positive correlated with axial length(<i>r</i>=0.681, <i>P</i><0.05). <p>CONCLUSION: In the study, patients with high myopia tend to have early onset, low educational level, and spacious living environment. Such results indicate that the genetic factors may be the main cause of high myopia in this group. The higher the degree of myopia was, the worse BCVA and the longer AL would be

Contact interaction analysis of pion GTMDs

A contact interaction is used to calculate an array of pion twist-two, -three and -four generalised transverse light-front momentum dependent parton distribution functions (GTMDs). Despite the interaction's simplicity, many of the results are physically relevant, amongst them a statement that GTMD size and shape are largely prescribed by the scale of emergent hadronic mass. Moreover, proceeding from GTMDs to generalised parton distributions (GPDs), it is found that the pion's mass distribution form factor is harder than its electromagnetic form factor, which is harder than the gravitational pressure distribution form factor; the pressure in the neighbourhood of the pion's core is commensurate with that at the centre of a neutron star; the shear pressure is maximal when confinement forces become dominant within the pion; and the spatial distribution of transversely polarised quarks within the pion is asymmetric. Regarding transverse momentum dependent distribution functions (TMDs), their magnitude and domain of support decrease with increasing twist. The simplest Wigner distribution associated with the pion's twist-two dressed-quark GTMD is sharply peaked on the kinematic domain associated with valence-quark dominance; has a domain of negative support; and broadens as the transverse position variable increases in magnitude.Comment: 20 pages, 12 figures, 1 tabl