Association between congenital hypothyroidism and in-hospital adverse outcomes in very low birth weight infants / 中华儿科杂志

Objective: To investigate the association between congenital hypothyroidism (CH) and the adverse outcomes during hospitalization in very low birth weight infants (VLBWI). Methods: This prospective, multicenter observational cohort study was conducted based on the data from the Sino-northern Neonatal Network (SNN). Data of 5 818 VLBWI with birth weight <1 500 g and gestational age between 24-<37 weeks that were admitted to the 37 neonatal intensive care units from January 1st, 2019 to December 31st, 2022 were collected and analyzed. Thyroid function was first screened at 7 to 10 days after birth, followed by weekly tests within the first 4 weeks, and retested at 36 weeks of corrected gestational age or before discharge. The VLBWI were assigned to the CH group or non-CH group. Chi-square test, Fisher exact probability method, Wilcoxon rank sum test, univariate and multivariate Logistic regression were used to analyze the relationship between CH and poor prognosis during hospitalization in VLBWI. Results: A total of 5 818 eligible VLBWI were enrolled, with 2 982 (51.3%) males and the gestational age of 30 (29, 31) weeks. The incidence of CH was 5.5% (319 VLBWI). Among the CH group, only 121 VLBWI (37.9%) were diagnosed at the first screening. Univariate Logistic regression analysis showed that CH was associated with increased incidence of extrauterine growth retardation (EUGR) (OR=1.31(1.04-1.64), P<0.05) and retinopathy of prematurity (ROP) of stage Ⅲ and above (OR=1.74(1.11-2.75), P<0.05). However, multivariate Logistic regression analysis showed no significant correlation between CH and EUGR, moderate to severe bronchopulmonary dysplasia, grade Ⅲ to Ⅳ intraventricular hemorrhage, neonatal necrotizing enterocolitis in stage Ⅱ or above, and ROP in stage Ⅲ or above (OR=1.04 (0.81-1.33), 0.79 (0.54-1.15), 1.15 (0.58-2.26), 1.43 (0.81-2.53), 1.12 (0.70-1.80), all P>0.05). Conclusion: There is no significant correlation between CH and in-hospital adverse outcomes, possibly due to timely diagnosis and active replacement therapy.

Reductant-dependent DNA-templated silver nanoparticle formation kinetics.

DNA molecules have been demonstrated to be good templates for producing silver nanoparticles (AgNPs), with the advantages of well-controlled sizes, shapes, and properties. Revealing the formation kinetics of DNA-templated AgNPs is crucial for their efficient synthesis. Herein, using magnetic tweezers, we studied the reduction kinetics of the Ag+-DNA structure and the subsequent nucleation kinetics by adding NaBH4, L-ascorbic acid, and sodium citrate solutions. At [Ag+] = 0.01 mM, the addition of NaBH4 solution with the same concentration resulted in the restoration of DNA. In contrast, by increasing the [NaBH4]/[Ag+] ratio (r) to 10 and 100, the DNA extension initially decreased rapidly and then increased, indicating nucleation-dissolution kinetics. With AgNO3 solutions of higher concentrations (0.1 mM and 1 mM), direct particle nucleation and growth kinetics were observed by adding a tenfold (r = 10) or a hundredfold (r = 100) amount of NaBH4, which were evidenced by a significant reduction in DNA extension. The reductant dependence of the kinetics was further investigated. Addition of L-ascorbic acid to the DNA-Ag+ solution yielded an increase-decrease kinetics that was different from that caused by NaBH4, suggesting that nucleation was not initially favored due to the lack of sufficient Ag atoms; while sodium citrate showed a weak nucleation-promoting ability to form AgNPs. We discussed the findings within the framework of classical nucleation theory, in which the supersaturation of the Ag atom is strongly influenced by multiple factors (including the reducing ability of the reductant), resulting in different kinetics.

Tensor Network Efficiently Representing Schmidt Decomposition of Quantum Many-Body States.

Efficient methods to access the entanglement of a quantum many-body state, where the complexity generally scales exponentially with the system size N, have long been a concern. Here we propose the Schmidt tensor network state (Schmidt TNS) that efficiently represents the Schmidt decomposition of finite- and even infinite-size quantum states with nontrivial bipartition boundary. The key idea is to represent the Schmidt coefficients (i.e., entanglement spectrum) and transformations in the decomposition to tensor networks (TNs) with linearly scaled complexity versus N. Specifically, the transformations are written as the TNs formed by local unitary tensors, and the Schmidt coefficients are encoded in a positive-definite matrix product state (MPS). Translational invariance can be imposed on the TNs and MPS for the infinite-size cases. The validity of Schmidt TNS is demonstrated by simulating the ground state of the quasi-one-dimensional spin model with geometrical frustration. Our results show that the MPS encoding the Schmidt coefficients is weakly entangled even when the entanglement entropy of the decomposed state is strong. This justifies the efficiency of using MPS to encode the Schmidt coefficients, and promises an exponential speedup on the full-state sampling tasks.

Lanthanide ions induce DNA compaction with ionic specificity.

Lanthanide (Ln) cations exhibit unique properties that include the ability to interact with DNA to form metal-DNA complexes, which are of great interest in medical, biological and nano-technological fields. Both experimental and theoretical studies have not completely addressed the interaction dynamics between lanthanide ions and DNA. The present study investigates the dynamics of the Ln3+-DNA interaction at the level of a single DNA molecule. Different DNA-metal complexes were produced by the addition of the five lanthanide ions, La3+, Ce3+, Pr3+, Tb3+, and Ho3+ to the DNA solutions. The binding dynamics indicated that the lanthanide cations can induce DNA compaction in a concentration and force-dependent manner. Ionic specificity was displayed in the single-molecule interaction dynamics, where, Ho3+ was found to be the most efficient lanthanide to cause DNA compaction, which was verified by the morphological characterization. The DNA molecules in the five Ln3+-DNA complex solutions were restored to their original length with different restoration speeds, by the addition of EDTA, and this further indicated that the Ho3+ ion had the strongest affinity toward DNA. We conclude that counterion correlation cannot solely explain the ion-dependent DNA compaction, and ionic specificity should be considered significant.

Single Molecular Chelation Dynamics Reveals That DNA Has a Stronger Affinity toward Lead(II) than Cadmium(II).

Lead ions can bind to DNA via nonelectrostatic interactions and hence alter its structure, which may be related to their adverse effects. The dynamics of Pb2+-DNA interaction has not been well understood. In this study, we report the monomolecular dynamics of the Pb2+-DNA interaction using a magnetic tweezers (MT) setup. We found that lead cations could induce DNA compaction at ionic strengths above 1 µM, which was also confirmed by morphology characterization. The chelation behavior of the Pb2+-DNA and the Cd2+-DNA complex solutions after adding EDTA were compared. The results showed that EDTA chelated with the bound metal ions on DNA and consequently led to restoring the DNA to its original length but with different restoration speeds for the two solutions. The fast binding dynamics and the slower chelation dynamics of the Pb2+ scenario compared to that of Cd2+ suggested that Pb2+ was more capable to induce DNA conformational change and that the Pb2+-DNA complex was more stable than the Cd2+-DNA complex. The stronger affinities for DNA bases and the inner binding of lead cations were two possible causes of the dynamics differences. Three agents, including EDTA, sodium gluconate, and SDBS, were used to remove the bound lead ions on DNA. It was shown that EDTA was the most efficient, and sodium gluconate could not fully restore DNA from its compact state. We concluded that both EDTA and SDBS were good candidates to restore the Pb2+-bound DNA to its original state.

Cold atoms meet lattice gauge theory.

The central idea of this review is to consider quantum field theory models relevant for particle physics and replace the fermionic matter in these models by a bosonic one. This is mostly motivated by the fact that bosons are more 'accessible' and easier to manipulate for experimentalists, but this 'substitution' also leads to new physics and novel phenomena. It allows us to gain new information about among other things confinement and the dynamics of the deconfinement transition. We will thus consider bosons in dynamical lattices corresponding to the bosonic Schwinger or [Formula: see text] Bose-Hubbard models. Another central idea of this review concerns atomic simulators of paradigmatic models of particle physics theory such as the Creutz-Hubbard ladder, or Gross-Neveu-Wilson and Wilson-Hubbard models. This article is not a general review of the rapidly growing field-it reviews activities related to quantum simulations for lattice field theories performed by the Quantum Optics Theory group at ICFO and their collaborators from 19 institutions all over the world. Finally, we will briefly describe our efforts to design experimentally friendly simulators of these and other models relevant for particle physics. This article is part of the theme issue 'Quantum technologies in particle physics'.

Phase identification in many-body systems by virtual configuration binarization.

Artificial intelligence provides an unprecedented perspective for studying phases of matter in condensed-matter systems. Image segmentation is a basic technique of computer vision that belongs to a branch of artificial intelligence. Inspired by the image segmentation techniques, in this work, we propose a scheme named virtual configuration binarization (VCB) to unveil quantum phases and quantum phase transitions in many-body systems. By encoding the information of renormalized quantum states into a color image and binarize the color image through the VCB, the renormalized quantum states can be visualized, from which quantum phase transitions can be revealed and the corresponding critical points can be identified. Our scheme is benchmarked on several strongly correlated spin systems, which does not depend on the priori knowledge of order parameters of quantum phases. This demonstrates the potential to disclose the underlying structure of quantum phases by the techniques of computer vision.

Mediating effect of milk intake between family socioeconomic status and body mass index of children and adolescents / 北京大学学报(医学版)

OBJECTIVE@#To examine the association between family socioeconomic status (SES) and body mass index (BMI) z-score of children and adolescents, and the mediating effect of milk intake in this association.@*METHODS@#In the study, 2 496 students and their parents were selected from 16 schools (4 urban middle schools, 4 rural middle schools, 4 urban primary schools, and 4 rural primary schools) using a stratified cluster sampling method. The frequency and amount of weekly milk intake from the 7-day Food Records reported by the students were extracted. The parents' education and household income were the indicators of family SES. The mediating effect of milk intake between family SES and BMI z-score of children and adolescents were tested using the PROCESS add-on SPSS software.@*RESULTS@#Parents' education level and household income were positively correlated with BMI z-score of children and adolescents (P=0.001 and 0.038, respectively). The overall average daily intake of milk was (0.92±0.84) servings, and the frequency was (4.43±2.70) days per week. The students of primary school, in urban areas, with higher parents' education level, with higher household income, and being non-obese were likely to have higher frequency and amount of milk intake. Milk intake was one of the mediating factors in the relationship between family SES and BMI z-score of children and adolescents. Specifically, the mediating effect of the frequency of milk intake accounted for -6.57% and -10.21% of the total effects of the association between the parents' education and the household income with BMI z-score of children and adolescents, respectively. The mediating effect of the daily intake of milk accounted for -3.63% and -5.86% of the total effects of the association between the parents' education and the household income with BMI z-score of children and adolescents, respectively.@*CONCLUSION@#The milk intake of Chinese children and adolescents still needs to be improved. High family SES was found to contribute to high BMI z-score, mediated by the milk intake which was the protective factors of BMI z-score. Further research is needed to study other dietary or physical exercise behaviors that mediate the relationship between family SES and BMI z-score of children and adolescents in order to adopt more targeted interventions.

Tangent-space gradient optimization of tensor network for machine learning.

The gradient-based optimization method for deep machine learning models suffers from gradient vanishing and exploding problems, particularly when the computational graph becomes deep. In this work, we propose the tangent-space gradient optimization (TSGO) for probabilistic models to keep the gradients from vanishing or exploding. The central idea is to guarantee the orthogonality between variational parameters and gradients. The optimization is then implemented by rotating the parameter vector towards the direction of gradient. We explain and test TSGO in tensor network (TN) machine learning, where TN describes the joint probability distribution as a normalized state |ψ〉 in Hilbert space. We show that the gradient can be restricted in tangent space of 〈ψ|ψ〉=1 hypersphere. Instead of additional adaptive methods to control the learning rate η in deep learning, the learning rate of TSGO is naturally determined by rotation angle θ as η=tanθ. Our numerical results reveal better convergence of TSGO in comparison to the off-the-shelf Adam.

Divalent metal ions and intermolecular interactions facilitate DNA network formation.

The interactions between divalent metal ions and DNA are crucial for basic life processes. These interactions are also important in advanced technological products such as DNA-based ion sensors. Current polyelectrolyte theories cannot describe these interactions well and do not consider the corresponding dynamics. In this study, we report the single-molecule dynamics of the binding of divalent metal ions to a single DNA molecule and the morphology characterization of the complex. We found that most of the divalent metal ions (Mn2+, Zn2+, Co2+, Ni2+, and Cd2+), except Mg2+ and Ca2+, could cause monomolecular DNA condensation. For transition metal ions, different ionic strengths were required to induce the compaction, and different shortening speeds were displayed in the dynamics, indicating ionic specificity. Atomic force microscopy revealed that the morphologies of the metal ion-DNA complexes were affected by the ionic strength of the metal ion, DNA chain length, and DNA concentration. At low metal ion concentration, DNA tended to adopt a random coil conformation. Increasing the ionic strength led to network-like condensed structures, suggesting that divalent metal ions can induce attraction between DNA molecules. Furthermore, higher DNA concentration and longer chain length enhanced intermolecular interactions and consequently resulted in network structures with a higher degree of interconnectivity.

In vitro immune response of insulin-like growth factor 2 mRNA-binding protein 3 restricted cytotoxic T lymphocyte epitope from lung cancer immunotherapy target / 解剖学报

Objective Cancer immunotherapy is attractive for antigen-specific T cell-mediated anti-tumor therapy, especially in induction of cytotoxic T lymphocytes(CTL). In this report, we evaluated insulin-like growth factor 2 mRNA-binding protein 3(IGF2P3) restricted epitope-induced cytotoxic T lymphocytes effects in human lung cancer cells. Methods The human leukocyte antigen A2(HLA-A2) restricted epitope peptides of IGF2P3 were selected by NetCTL 1. 2, SYFPEITHI and IEDB software prediction. The binding affinity of the peptides to HLA-A02 molecules was evaluated by T2A2 cells binding assay. enzyme-linked immunosport(ELISPOT) assay was used to investigate the ability of the peptide to induce specific restricted cytotoxic T lymphocytes (CTL) and release of interferon γ(IFN-γ). The ability of the peptides to induce T cell response was investigated by carboxyfluorescein succinimidyl amino ester (CFSE) fluorescent staining. Results The candidate peptide P143, P199, P280, P409 and P515 showed moderate affinity toward HLA-A2 molecule. ELISPOT assay showed P409, P515 were able to induce specific CTL and higher levels of IFN-γ were released. The CTL induced by P409, P515 lysed target cells. Conclusion P409 and P515 have the potential for adoptive immunotherapy and can be used as candidate epitopes for new anti-tumor polypeptide immunotherapy vaccine. P409 and P515 can be used in peptide-based immunotherapy for lung cancer.

Multistage dynamics of Hg2+-DNA interactions: a single-molecule study.

The metal ion-DNA interaction is key to biochemical processes and has applications in areas such as metal ion sensors and DNA nanomachines. For example, the formation of the T-Hg2+-T structure has been used in technologies such as DNA-based mercuric ion sensors. Though the interaction is widely used for practical purposes, the underlying mechanism has not been fully understood. In the present study, we used magnetic tweezers to explore the interactions between λ-DNA and two metal ions, Hg2+ and Cd2+, at the single-molecule level. Both metal ions caused considerable DNA conformational changes. The resulting DNA compaction dynamics were related to the ion concentration and the exerted force. The increase in the ion concentration promoted DNA compaction, whereas exerting greater forces inhibited this process. Application of a high force generated two-stage dynamics of the Hg2+-DNA interaction. However, at a sufficiently high Hg2+ concentration, a lower force led to a three-stage process. In contrast, the curves of the binding of Cd2+ ions to DNA had a stepwise pattern. Both the AFM scanning results and the single-molecule measurements confirmed that Hg2+ influences the DNA conformation in a more pronounced manner than Cd2+. The multistage Hg2+-DNA interaction was considered to be a result of the different binding mechanisms, including the mismatched base-pair formation. A model was then proposed to explain the peculiar dynamics.

Proliferation of MicroRNA-365 and E74-like Factor 4 in Cervical Cancer Cells and Its Clinical Significance / 中国医学科学院学报

Objective To investigate the expressions,roles,and clinical significance of microRNA-365(miR-365)and E74-like factor 4(ELF4)in cervical cancer. Methods The expressions of miR-365 in normal cervical tissues(n=34),cervical intraepithelial neoplasia 1(CIN 1)(n=31),cervical intraepithelial neoplasia2-3(CIN 2-3)(n=37),squamous cell carcinoma of the cervix(SCC)(n=33),and three cervical cancer cell lines(C33A cells,Hela cells,and SiHa cells)were detected by real-time quantitative polymerase chain reaction(qPCR).Bioinformatic prediction and luciferase reporter gene assay were performed to verify whether ELF4 was a direct target of miR-365.Western blot and immunohistochemistry were used to detect ELF4 expression in cervical cancer cells and in different pathological cervix tissues.CCK8 assay was used to detect the effect of overexpression or inhibition of miR-365 on the proliferation of cervical cancer cells at different time points.The relationships among the miR-365 expression,ELF4 expression,and clinicopathological parameters of cervical cancer were analyzed by correlation analysis. Results qPCR results showed that compared with the normal cervical cell HcerEpic,the expressions of miR-365 in CIN1,CIN2-3,and cervical cancer tissues gradually decreased with the increased pathologic grade,and its expressions also decreased in different cervical cancer cell lines.The luciferase reporter gene assay confirmed that ELF4 was the direct target of miR-365.Western blot showed that the expression of ELF4 increased in all three cervical cancer cell lines compared with normal cervical epidermal cell(P=0.013,P=0.002,P=0.004).Immunohistochemistry showed that ELF4 expression was up-regulated in CIN and cervical cancer tissues.CCK8 assay showed that overexpression of miR-365 inhibited cell proliferation,while inhibition of miR-365 promoted the proliferation of three cervical cancer cells(PConclusion The decreased expression of miR-365 in human cervical cancer cells relieves its inhibitory effect on ELF4,which promotes the proliferation of cervical cancer cells and the formation of tumor.

Two-stage DNA compaction induced by silver ions suggests a cooperative binding mechanism.

The interaction between silver ions and DNA plays an important role in the therapeutic use of silver ions and in related technologies such as DNA sensors. However, the underlying mechanism has not been fully understood. In this study, the dynamics of Ag+-DNA interaction at a single-molecule level was studied using magnetic tweezers. AgNO3 solutions with concentrations ranging from 1 µM to 20 µM led to a 1.4-1.8 µm decrease in length of a single λ-DNA molecule, indicating that Ag+ has a strong binding with DNA, causing the DNA conformational change. The compaction process comprises one linear declining stage and another sigmoid-shaped stage, which can be attributed to the interaction mechanism. Considering the cooperative effect, the sigmoid trend was well explained using a phenomenological model. By contrast, addition of silver nanoparticle solution induced no detectable transition of DNA. The dependence of the interaction on ionic strength and DNA concentration was examined via morphology characterization and particle size distribution measurement. The size of the Ag+-DNA complex decreased with an increase in Ag+ ionic strength ranging from 1 µM to 1 mM. Morphology characterization confirmed that silver ions induced DNA to adopt a compacted globular conformation. At a fixed [AgNO3]:[DNA base pairs] ratio, increasing DNA concentration led to increased sizes of the complexes. Intermolecular interaction is believed to affect the Ag+-DNA complex formation to a large extent.

Thermodynamics of spin-1/2 Kagomé Heisenberg antiferromagnet: algebraic paramagnetic liquid and finite-temperature phase diagram.

Quantum fluctuations from frustration can trigger quantum spin liquids (QSLs) at zero temperature. However, it is unclear how thermal fluctuations affect a QSL. We employ state-of-the-art tensor network-based methods to explore the ground state and thermodynamic properties of the spin-1/2 kagomé Heisenberg antiferromagnet (KHA). Its ground state is shown to be consistent with a gapless QSL by observing the absence of zero-magnetization plateau as well as the algebraic behaviors of susceptibility and specific heat at low temperatures, respectively. We show that there exists an algebraic paramagnetic liquid (APL) that possesses both the paramagnetic properties and the algebraic behaviors inherited from the QSL. The APL is induced under the interplay between quantum fluctuations from geometrical frustration and thermal fluctuations. By studying the temperature-dependent behaviors of specific heat and magnetic susceptibility, a finite-temperature phase diagram in a magnetic field is suggested, where various phases are identified. This present study gains useful insight into the thermodynamic properties of the spin-1/2 KHA with or without a magnetic field and is helpful for relevant experimental studies.

In vivo immunogenic characteristics of cytotoxic T lymphocyte epitopes from pancreatic tumor antigen MUC4 / 中国病理生理杂志

AIM:Peptide vaccines have been conceived as promising therapies for tumor-inflicted patients due to their easy production and capability of inducing specific immune response required for defending the tumor.During our previous research,4 HLA-A2-restricted peptides had been identified as immunogenic in vivo.In this study, we aimed to testify the in vivo immunogenicity of the 4 peptides.METHODS: BALB/c mice were vaccinated with HLA-A2 restricted peptides emulsified in incomplete Freund's adjuvant(IFA)subcutaneously in combination with the epitope at the adjacent location.After the 3rd peptide vaccination for 10 d,the peptide-specific immune response was evaluated by ELISPOT and ELISA.The ability to induce T cell response was investigated by using cytotoxicity assay in vivo and the presence of pep-tide-specific CD8+T cells capable of recognizing the MHC-peptide was detected by flow cytometry.RESULTS: Among the 4 candidate HLA-A2 restricted peptides,the immune response elicited by P2004-1Y9V was superior to that of the other 3 peptides.The CTLs induced by P2004 and P2004-1Y9V lysed CAPAN-2 cells.P2004-1Y9V peptide-specific CTLs showed higher cytotoxicity against pancreatic tumor cell lines of CAPAN-2 than the native peptide-specific CTLs.Intracellu-lar cytokine staining assay indicated the presence of P 2004-1Y9V specific CD8 +T cells in the P2004-1Y9V vaccinated mice.CONCLUSION:P2004-1Y9V is the most immunogenic peptide in vivo, and can be explored as potential tumor peptide vaccine in the future clinical study.

Identification and molecular modification of cytotoxic T-lymphocyte epitopes from osteosarcoma high-expressing antigen PBF / 中国病理生理杂志

AIM:To observe whether modified epitopes from osteosarcoma high-expressing antigen papilloma-virus-binding factor (PBF) have HLA-A2 restricted antitumor ability,and to develop peptide-based immunotherapy for os-teosarcoma. METHODS:RT-PCR and Western blot were used to determine the expression of PBF in the osteosarcoma cell lines U2OS and Saos-2. HLA-A2 epitopes from PBF protein were predicted by NetCTL 1.2, SYFPEITHI and IEDB. The modified peptides from PBF containing HLA-A2 binding anchor motifs were designed by replacing the anchor residues. The peptides were synthesized by standard solid-phase methods,and the binding affinity of the peptides to HLA-A?0201 was evaluated by T2A2 cell binding assay. ELISPOT assay was used to investigate the seretion of interferon-γ(IFN-γ) from the peptide-induced specific cytotoxic T-lymphocytes (CTLs). The ability of inducing T-cell response was analyzed by lactate dehydrogenase (LDH) release assay and carboxyfluorescein succinimidyl ester (CFSE) cytotoxicity assay in vitro. RE-SULTS:The expression of PBF was observed in the U2OS and Saos-2 cells. The candidate peptides P75-1Y2L,P412-1Y, P416-1Y2L9V, P107-1Y and P435-1Y2L showed moderate affinity toward HLA-A2 molecule. The modified peptides showed significantly higher affinity with HLA-A2 than the native peptide. ELISPOT assay showed that P412, P412-1Y, P416,P416-1Y2L9V and P435-1Y2L induced specific CTLs to secrete IFN-γ, and P412-1Y and P416-1Y2L9V induced more secretion of IFN-γ than the native peptide. The CTLs induced by P412, P412-1Y, P416 and P416-1Y2L9V lysed U2OS cells. P412-1Y and P416-1Y2L9V peptide-specific CTLs showed higher cytotoxicity against U2OS cells than the native peptide-specific CTLs. CONCLUSION:Compared with the native peptide,modified epitopes P412-1Y and P416-1Y2L9V have higher binding affinity with HLA-A?0201 and retain immunogenecity. In addition,the anti-tumor immunity effects of modified epitopes P412-1Y and P416-1Y2L9V are stronger than the native peptide. The peptides P412-1Y and P416-1Y2L9V is excellent HLA-A?0201 restricted CTL epitopes from tumor antigen PBF,which could serve as new can-didates towards antitumor peptide vaccines.

Mutational analysis and stability characterization of a novel esterase of lipolytic enzyme family VI from Shewanella sp.

Esterases are widely used in different industries. Here, a novel esterase, Esth, with low identity with previously reported esterases, was identified and characterized. The results showed that Esth was a cold-adapted esterase and retained 50% of its maximum activity at 0°C. Besides, Esth showed great activity and stability in high concentrations of NaCl. When treated with some organic solvents, detergents and metal ions, Esth showed high activity as well. The kcat/Km value of Esth was 29.5s-1mM-1, suggesting that it has higher catalytic efficiency than all the previously reported esterases from the same family, lipolytic enzyme family VI. The structural modeling showed that changing Ala129 into Gly would form a new hydrogen bond between ser125 and Gly129 and make theα-helix longer, which might influence on the thermostability of enzymes (Kumar, 2000). To confirm this, the mutant EsthA129G was obtained by site-directed mutagenesis. The result indicated that EsthA129G retained over 70% of the activity versus 12% for Esth after incubation at 55°C for 120min, showed a nearly six fold increase when compared with wild type. Overall, Esth shows a potential application prospect in extreme conditions and the mutation research can provide some structural information about thermostable enzymes.

Ab initio optimization principle for the ground states of translationally invariant strongly correlated quantum lattice models.

In this work, a simple and fundamental numeric scheme dubbed as ab initio optimization principle (AOP) is proposed for the ground states of translational invariant strongly correlated quantum lattice models. The idea is to transform a nondeterministic-polynomial-hard ground-state simulation with infinite degrees of freedom into a single optimization problem of a local function with finite number of physical and ancillary degrees of freedom. This work contributes mainly in the following aspects: (1) AOP provides a simple and efficient scheme to simulate the ground state by solving a local optimization problem. Its solution contains two kinds of boundary states, one of which play the role of the entanglement bath that mimics the interactions between a supercell and the infinite environment, and the other gives the ground state in a tensor network (TN) form. (2) In the sense of TN, a novel decomposition named as tensor ring decomposition (TRD) is proposed to implement AOP. Instead of following the contraction-truncation scheme used by many existing TN-based algorithms, TRD solves the contraction of a uniform TN in an opposite way by encoding the contraction in a set of self-consistent equations that automatically reconstruct the whole TN, making the simulation simple and unified; (3) AOP inherits and develops the ideas of different well-established methods, including the density matrix renormalization group (DMRG), infinite time-evolving block decimation (iTEBD), network contractor dynamics, density matrix embedding theory, etc., providing a unified perspective that is previously missing in this fields. (4) AOP as well as TRD give novel implications to existing TN-based algorithms: A modified iTEBD is suggested and the two-dimensional (2D) AOP is argued to be an intrinsic 2D extension of DMRG that is based on infinite projected entangled pair state. This paper is focused on one-dimensional quantum models to present AOP. The benchmark is given on a transverse Ising chain and 2D classical Ising model, showing the remarkable efficiency and accuracy of the AOP.

Polyethylene glycol and divalent salt-induced DNA reentrant condensation revealed by single molecule measurements.

In this study, we investigated the DNA condensation induced by polyethylene glycol (PEG) with different molecular weights (PEG 600 and PEG 6000) in the presence of NaCl or MgCl2 by using magnetic tweezers (MT) and atomic force microscopy (AFM). The MT measurements show that with increasing NaCl concentration, the critical condensation force in the PEG 600-DNA or PEG 6000-DNA system increased approximately linearly. PEG 6000 solution has a larger critical force than PEG 600 solution at a given NaCl concentration. In comparison, a parabolic trend of the critical condensation force was observed with increasing MgCl2 concentration, indicating that DNA undergoes a reentrant condensation. The AFM results show that the morphologies of the compacted DNA-PEG complexes depended on the salt concentration and were consistent with the MT results.