fFabrication of three-dimensional proteinaceous micro- and nano-structures by femtosecond laser cross-linking

Proteins are a class of biomaterials having a vast array of functions, including the catalysis of metabolic reactions, DNA replication, stimuli response and transportation of molecules. Recent progress in laser-based fabrication technologies has enabled the formation of three-dimensional （3D） proteinaceous micro- and nano-structures by femtosecond laser cross-linking, which has expanded the possible applications of proteins. This article reviews the current knowledge andrecent advancements in the femtosecond laser cross-linking of proteins. An overview of previous studies related to fabri-cation using a variety of proteins and detailed discussions of the associated mechanisms are provided. In addition, ad-vances and applications utilizing specific protein functions are introduced. This review thus provides a valuable summaryof the 3D micro- and nano-fabrication of proteins for biological and medical applications.

RNA binding protein BOULE forms aggregates in mammalian testis

Amyloids have traditionally been considered pathologic protein aggregates which contribute to neurodegeneration.New evidence however increasingly suggests that non-pathological amyloids are formed in animals during normal development.Amyloid-like aggregate formation was originally thought to be a conserved feature of animal gametogenesis.This hypothesis was based on findings which suggest that regulated amyloid formations govern yeast meiosis by way of meiosis-specific RNA binding proteins.Additional support came from studies which demonstrate that DAZL,a mammalian gametogenesis-specific RNA binding protein,also forms SDS-resistant aggregates in vivo.Here,we report evidence of aggregated BOULE formations,another DAZ family protein,during sperm development.Data suggest that in mouse testis,BOULE forms SDS-resistant amyloid-like aggregates.BOULE aggregate formation correlates with dynamic developmental expression during spermatogenesis but disappeared in Boule knockout testis.We also mapped essential small region in vitro BOULE aggregations,immediately downstream DAZ repeats,and found that aggregations positively correlated with temperature.We also performed enhanced UV cross-linking immunoprecipitation on BOULE aggregates from mouse testes and found that aggregates bind with a large number of spermatogenesis-related mRNAs.These findings provide insight into the amyloidogenic properties of gametogenesis-specific RNA binding proteins as a conserved feature in mammalian reproduction.Further investigation is warranted to understand the functional significance of BOULE amyloid-like formation during mouse spermatogenesis.

Secondary structure characterization of mixed food protein complexes using microfluidic modulation spectroscopy(MMS)

Microfluidic modulation spectroscopy(MMS)has been recognised as a novel technology for producing high quality and reproducible data at a wide concentration range to characterise protein structure.In this study,the use of MMS for food applications was explored through the structural analysis of pea protein,whey protein,and pea/whey protein complexes prepared by transglutaminase cross-linking.MMS generated reproducible data with>99.5%repeatability in all protein samples.The cross-linking seemed to alter the structure of whey protein with isopeptide and hydrogen bond formation,more significantly than that of pea protein.The larger secondary and tertiary structural changes were observed with higher whey protein content in cross-linked pea/whey protein complex,which eventually increased the surface hydrophobicity.According to the second derivatives analysis by MMS,β-sheet and random coil increased andβ-turn decreased in the pea protein,whereasα-helix,β-sheet,andβ-turn decreased and random coil increased in the whey protein after cross-linking.In the pea/whey protein complex,β-turn shifted toβ-sheet due to cross-linking.There are some discrepancies between the relative secondary structure contents obtained from MMS data compared to the data acquired from circular dichroism.However,MMS has the considerable advantage of being able to directly measure original samples without significant dilution as required for circular dichroism measurements.This study provides evidence that MMS technology could be a robust technique to quantify the secondary structures of typical proteins in food with high reliability.

5-Hexylidene-4-propylamino-1,5-dihydroimidazol-2-one formed from Cu-catalyzed oxidation with implication for the structure of a His-Lys cross-link

Cu-catalyzed oxidation of 5-hexyl-1,3-dihydroimidazo-2-one (1) in the presence of propylamine, as surrogates for the oxidized His side chain and Lys side chain, was investigated. 5-Hexylidene-4-propylamino-1,5-dihydroimidazol-2-one (2), a model His-Lys cross-link product, was isolated and structurally characterized by NMR and mass spectrometry.

Buckling of filamentous actin bundles in filopodial protrusion

The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.

何首乌对老龄大鼠大脑皮层蛋白质含量的影响

衰老的交联学说认为:随着年龄的增长,体内生物大分子通过共价键不断连接形成难以分解的聚合物。这些聚合物失去了原有分子的生物活性,从而使机体老化。随龄增加的自由基反应是交联形成的重要原因。中药何首乌是传统的抗衰老药物。最近的研究发现其能提高老龄机体的抗氧化能力。因此,何首乌有可能影响体内大分子的交联。本实验通过对大鼠大脑皮层总蛋白、水溶性蛋白及非水溶性蛋白含量的测定,观察何首乌是否能影响大脑皮层蛋白质的交联作用。

Tightening up the structure, lighting up the pathway:application of molecular constraints and light to manipulate protein folding, self-assembly and function

Chemical cross-linking provides an effective avenue to reduce the conformational entropy of polypeptide chains and hence has become a popular method to induce or force structural formation in peptides and proteins.Recently,other types of molecular constraints,especially photoresponsive linkers and functional groups,have also found increased use in a wide variety of applications.Herein,we provide a concise review of using various forms of molecular strategies to constrain proteins,thereby stabilizing their native states,gaining insight into their folding mechanisms,and/or providing a handle to trigger a conformational process of interest with light.The applications discussed here cover a wide range of topics,ranging from delineating the details of the protein folding energy landscape to controlling protein assembly and function.

Advances of Coagulation Factor XIII

Objective： To provide a comprehensive literature review on roles of coagulation factor XIII （FXIII） in coagulation, wound healing, neoplasm, bone metabolism, and pregnancy. Data Sources： All articles in PubMed with key words ＂Coagulation factor XIII＂, ＂wound＂, ＂＇leukeraia＂, ＂tumor＂, ＂bone,＂ and ＂pregnancy＇＂ with published date from 2001 to 2016 were included in the study. Frequently cited publications before 2000 were also included. Study Selection： We reviewed the role of FXIll in biologic processes as documented in clinical, animal, and in vitro studies. Results： FXIII, a nlember of the transglutaminase （TG） family, plays key roles in various biological processes. Besides its well-known function in coagulation, the cross-linking of small molecules catalyzed by FXIII has been found in studies to help promote wound healing, improve bone metabolism, and prevent miscarriages. The study has also shown that FXIII concentration level differs in the blood of patients with leukemia and solid tumors and offers promises as a diagnostic indicator Conclusions： FXIII has many more biologic functions besides being known as coagulation factor. The TG activity of FXIII contributes to several processes, including wound healing, bone extracellular matrix stabilization, and the interaction between embryo and decidua of uterus. Further research is needed to elucidate the link between FXIII and leukemia and solid tumors.