Synthesis of Functional Polypeptides and Development of New Synthetic Strategies toward Polypeptides

The objective of this work is to develop a new synthetic strategy for synthesizing advanced functional polypeptides or polypeptides in general. Polypeptides are amino acids based polymers with appealing properties for different applications. One of the key challenges in polypeptide research is the synthesis of functional polypeptides under mild conditions. We developed a system based on ring-opening polymerization (ROP) of N-thiocarboxyanhydrosulfides (NTAs) to synthesize polypeptides with wide range of molecular weights under mild conditions. Owing to NTAs’ good stability, our system serves as an excellent alternative to the traditional ROP of N-carboxyanhydrides (NCA). In Chapter 1, the fundamental knowledge and the cutting-edge research of polypeptides will be reviewed. The focus of the work in Chapter 2 is to develop a new class of functional polypeptide in traditional method via ROP of NCAs. This class of polypeptides combines several desired attributes for biomedical applications, which include: clickable pendant side chains for further functionalization, good water solubility, non-ionic nature to avoid unspecific interactions in biological systems, and unique secondary conformations (e.g. α-helix, β-sheet). In Chapter 3, I developed the first system to prepare polypeptides with controlled molecular weight via primary amine initiated solid-phase ring-opening polymerization (sROP) of NTAs under mild conditions in open air. Model NTA (e.g. BLG NTA, LYS NTA) monomers were synthesized for the first time, and were found to possess better thermal and moisture stability as compared to NCA analogs. The sROP proceeds by a normal amine mechanism as evidenced by matrix assisted light desorption ionization time of flight mass spectroscopy (MALDI-TOF MS). The controlled polymerization behavior of sROP is the direct result of high local monomer concentration in the solid phase, thus allowing for faster polymerization under relatively mild conditions. The work in Chapter 4 focuses on the development of solution phase polymerization of NTAs with TMG/benzoic acid as co-initiation system. PBLG with high molecular weights (33.6 kg/mol - 66.7 kg/mol) and narrow molecular weight distribution (PDI \u3c 1.12) can be readily prepared with this system. The mechanism of the TMG/benzoic acid mediated ROP of NTAs is proposed to be activated monomer mechanism (AMM)

Giant reversible elongation upon cooling and contraction upon heating for a crosslinked cis poly(1,4-butadiene) system at temperatures below zero Celsius

Abstract Polymers with reversible elongation upon cooling (EUC) and contraction upon heating (CUH) enabled applications in actuators, fasteners, dampers, grippers, swimmers, sealants, etc. With the current working temperature being limited to mainly above zero Celsius, applications for subzero Celsius environments are obstructed. In addition, current reversible actuation needs a constant tensile load, or for the best case, under zero tensile load. Reversible EUC and CUH under compressive load is almost impossible and has not been explored. In this work, a cis poly(1,4-butadiene) based system has been developed. Actuated below zero Celsius, 69% EUC occurred under a tensile load; and 6.2% EUC and 17.9% CUH occurred under 0.05 MPa compressive load. The reversible actuation was driven by both entropy and enthalpy, which was validated by a series of characterization tools

Prediction of Neutralization Depth of R.C. Bridges Using Machine Learning Methods

Machine learning techniques have become a popular solution to prediction problems. These approaches show excellent performance without being explicitly programmed. In this paper, 448 sets of data were collected to predict the neutralization depth of concrete bridges in China. Random forest was used for parameter selection. Besides this, four machine learning methods, such as support vector machine (SVM), k-nearest neighbor (KNN) and XGBoost, were adopted to develop models. The results show that machine learning models obtain a high accuracy (>80%) and an acceptable macro recall rate (>80%) even with only four parameters. For SVM models, the radial basis function has a better performance than other kernel functions. The radial basis kernel SVM method has the highest verification accuracy (91%) and the highest macro recall rate (86%). Besides this, the preference of different methods is revealed in this study

Enhanced Turbulent Mixing in the Upper Ocean Induced by Super Typhoon Goni (2015)

Based on the satellite-observed sea surface temperature (SST) data, high-resolution Argo observations and hybrid coordinate model (HYCOM) reanalysis results, this study examined the upper ocean response to Super Typhoon Goni in 2015 in the western north Pacific and revealed the significant diapycnal diffusivity enhancement in the upper ocean induced by Goni. Results indicate that the maximum SST cooling caused by Goni was 7.7 °C, which is greater than the SST cooling caused by most typhoons. The severe SST cooling was related to the enhancement of turbulent mixing induced by Goni. To the right of the typhoon track, the diapycnal diffusivity enhancement in the upper ocean caused by Goni could reach three orders of magnitude, from O (10−5 m2/s) to O (10−2 m2/s) and could last at least 9 days after the passage of Goni. In contrast, the diapycnal diffusivity to the left of the typhoon track did not show significant variations. The enhancement of turbulent mixing was found to be consistent with Goni-induced near-inertial kinetic energy calculated from the HYCOM reanalysis results, which suggests that the enhanced turbulent mixing was caused by Goni-induced near-inertial waves

Experimental Study on the In-Band Amplified Spontaneous Emission in the Single-Mode Continuous-Wave Yb-Doped Fiber Amplifier Operating near 980 nm

In this paper, the in-band amplified spontaneous emission (ASE) in the Yb-doped continuous-wave (CW) fiber amplifier operating near 980 nm is experimentally studied for the first time, to the best of our knowledge. A core-pumped single-mode Yb-doped fiber amplifier is fabricated and the effects of pump power, seed power, and active fiber length on the in-band ASE are investigated in the experiment. It is found that a strong in-band ASE around 980 nm can be observed even with no obvious ASE around 1030 nm present. It is also found that with the increment of pump power, the in-band ASE can be enhanced faster than the signal light. By studying the effects of seed power and active fiber length, it is found that, although increasing the seed power and shortening the active fiber can both suppress the in-band ASE, the latter method is less effective than the former one. The theoretical study is also carried out in order to understand the difference between the in-band ASE and 1030-nm ASE. The experimental observations are also discussed qualitatively with the theoretical results. We believe that the pertinent results and discussions can provide significant guidance for understanding the in-band ASE in the Yb-doped fiber amplifier operating near 980 nm

Full-Length Transcriptome Analysis of Skeletal Muscle of Jiangquan Black Pig at Different Developmental Stages

Skeletal muscle grows in response to a combination of genetic and environmental factors, and its growth and development influence the quality of pork. Elucidating the molecular mechanisms regulating the growth and development of skeletal muscle is of great significance to both animal husbandry and farm management. The Jiangquan black pig is an excellent pig breed based on the original Yimeng black pig, importing the genes of the Duroc pig for meat traits, and cultivated through years of scientific selection and breeding. In this study, full-length transcriptome sequencing was performed on three growth stages of Jiangquan black pigs, aiming to study the developmental changes in Jiangquan black pigs at different developmental stages at the molecular level and to screen the key genes affecting the growth of skeletal muscle in Jiangquan black pigs. We performed an enrichment analysis of genes showing differential expression and constructed a protein–protein interaction network with the aim of identifying core genes involved in the development of Jiangquan black pigs. Notably, genes such as TNNI2, TMOD4, PLDIM3, MYOZ1, and MYH1 may be potential regulators of muscle development in Jiangquan black pigs. Our results contribute to the understanding of the molecular mechanisms of skeletal muscle development in this pig breed, which will facilitate molecular breeding efforts and the development of pig breeds to meet the needs of the livestock industry

Design and Operating Parameters Optimization of the Hook-and-Tooth Chain Rail Type Residual Film Picking Device

We attempt to solve the current problems of high impurity content and the poor reliability of chain harrow type residual film recovery machines when picking up residual film. This study makes a device for picking up residual film with a hook-and-tooth chain rail. First, we conducted an analysis of the trajectory of the tip movement of the hooked teeth in the designed picking device, with the condition that the residual mulch does not miss the picking, and the force conditions of the residual mulch in the conveying process and the collection process are presented. Secondly, to determine the optimal working parameters of the picking device, a three-factor, three-level response surface optimization test was conducted with the machine forward speed, hook tooth entry depth, and chain harrow input speed as the test factors and the residual film picking rate and the impurity rate of residual film as the test indexes. In addition, a response surface regression model was developed to analyze the effects of the selected factors on the picking device. When the forward speed of the machine was 1.62 m/s, the hook tooth entry depth was 38.51 mm, and the input speed of the chain harrow was 241.42 rpm, the pickup rate and the impurity rate of the residual film were 88.27% and 9.96%, respectively. Finally, the simulation test was carried out under optimal working conditions, with the maximum force of the hook teeth being 60.7 N, the maximum deformation being 31.42 mm, and the maximum stress being 215.33 Mpa. This study can be used as a guide to further improve the design of the residual film recovery machine

Non-ionic water-soluble clickable α-helical polypeptides: Synthesis, characterization and side chain modification

© The Royal Society of Chemistry. A series of water-soluble non-ionic clickable polypeptides has been synthesized by organo-initiated ring-opening co-polymerization (ROP) of γ-propargyl-l-glutamic acid N-carboxyanhydride (PLG NCA) and N-ε-2-[2-(2-methoxyethoxy)ethoxy]acetyl-l-lysine N-carboxyanhydride (EG2-LYS NCA). The pendant alkyne side groups can be modified with azido-containing hydrophobic and hydrophilic bioactive moieties, producing polypeptide conjugates with good water solubility. Circular dichroism (CD) reveals that both the parent polypeptides and the modified polypeptide conjugates maintain high levels of α-helical conformations in aqueous solutions. A preliminary cell study indicated the cell binding peptide GRGDS (Gly-Arg-Gly-Asp-Ser) modified copolymers are able to induce integrin-mediated cell adhesion. This journal i