工科学校本科生科研训练与实践——以节能减排大赛为例

Scientific research training is an essential part of undergraduate learning, which plays an important role in improving students' knowledge utilization and scientific literacy. Taking the participation process of "Energy conservation and emission reduction competition" as an example, this paper briefly introduces the undergraduate scientific research training of students majoring in polymer materials and engineering from their own perspective, and the way to combine the discipline and school characteristics to reflect the thinking of engineering students in scientific research and practical application.     

First systematic investigation of C-H...Cl hydrogen bonding using inorganic supramolecular synthons: lamellar, stitched stair-case, linked-ladder, and helical structures

Using a group of six neutral M(II)Cl(2)-containing coordination compounds as building blocks, the first systematic investigation of C-H...Cl hydrogen-bonding interactions was performed. Single-crystal X-ray structural analyses of four new compounds (pseudo-tetrahedral Co(II) and Zn(II); distorted trigonal bipyramidal Zn(II)) authenticate the metal coordination geometry. To provide a unified view of the presence of noncovalent interactions in this class of compounds, we have re-examined the packing diagram of two previously reported compounds (a distorted square-pyramidal Cu(II) complex and a trans-octahedral Co(II) complex). The organic ligands of our choice comprise bidentate/tridentate pyrazolylmethylpyridines and an unsymmetrical tridentate pyridylalkylamine. This systematic investigation has allowed us to demonstrate the existence of versatile C-H...Cl(2)M interactions and to report the successful application of such units as inorganic supramolecular synthons. Additional noncovalent interactions such as C-H...O and O-H...Cl hydrogen bonding and pi-pi stacking interactions have also been identified. Formation of novel supramolecular architectures has been revealed: 2D lamellar (p-cyclophane) and 3D lamellar, 3D "stitched staircase" (due to additional hydrogen-bonding interactions by water tetramers, with an average O-O bond length in the tetramer unit of 2.926 A, acting as "molecular clips" between staircases), 3D linked ladder, and single-stranded 1D helix.     

新工科视阈下石油化工类高校应用化学专业课程体系重构

Taking a typical local and industry-orientated applied chemistry major as an example with focusing on the major changes in the form and content of the petrochemical industry, the way to reform the core curriculum system and teaching contents is presented. Based on the changing tendency of refinement of the petrochemical industry, a complete curriculum system with distinctive industry characteristics is set up according to the principles of the emerging engineering education (3E) with several reasonable suggestions. A new model for the construction of a 3E major in chemistry-related majors is suggested. It is a good reference for the construction of curriculum systems for other local and industry-orientated colleges who want to make 3E reform.     

Thermoanalytical study of nucleating effects in polypropylene composites

Nucleating and transcrystallization behaviour of additives in engineering PP composites and the effect of modified interfacial structure is the subject of this series of papers. The first part concentrates on polypropylene/liquid crystalline polyester blends. Increased crystallisation temperature and degree of crystallinity of polypropylene is characteristic to the blends containing different amount of LCP additive. Transcrystallization process governs the formation of crystalline structure in these systems in course of isothermal crystallisation at 132C. The nucleating effect of LCP gives rise to more uniform crystalline structure in the polypropylene phase.The financial support of the OTKA 014194 is acknowledged with gratitude.     

Selective formation of AAB- and ABC-type heterotrimeric alpha-helical coiled coils

The alpha-helical coiled coils have a representative amino acid sequence of (abcdefg)(n) heptad repeats. We previously reported that two peptides named IZ-2A and IZ-2W formed an (IZ-2A)(2)/IZ-2W heterotrimer with an Ala-Ala-Trp interaction in the hydrophobic core. In this paper, we describe the selective formation of AAB- and ABC-type heterotrimers. To increase the selectivity of the AAB-type heterotrimeric formation, Lys residues at the f position were mutated to either an Ala or a Gln residue to form IZ-2A(fA) or IZ-2W(fQ). Separately, both IZ-2A(fA) and IZ-2W(fQ) have a random structure at pH 7 and 20 degrees C. However, together IZ-2A(fA) and IZ-2W(fQ) form a 2:1 complex with a thermal transition midpoint (Tm) of 48 degrees C. This procedure was applied to prepare the ABC-type heterotrimer, in which two sets of Ala-Ala-Trp interactions were designed in the hydrophobic core. Interhelical interaction between the e and g positions and the alpha-helical propensity of the amino acid at the f position were also considered in the design. The resultant three peptides selectively formed the ABC-type heterotrimer with a Tm of 51 degrees C. Other peptide combinations had random coil properties.     

Anion control of isomerism, crystal packing and binding properties in a mononuclear zinc complex

The coordination chemistry of the tetradentate pyridyl N-donor ligand cis-3,5-bis-[2-pyridinyleneamin]-trans-hydroxycyclohexane (DDOP) has been investigated with zinc(II) nitrate and triflate. The resulting complexes, [Zn(DDOP)(H₂O)(NO₃)](NO₃) (1), and [Zn(DDOP)(H₂O)(OTf)](OTf) (2) differ not only in their counterions, but also the arrangement of the axial ligands and their solid state hydrogen bonded networks. Isothermal titration calorimetry was used to assess the difference in binding properties exhibited by the two zinc complexes at physiological pH in an aqueous environment. A series of coordinating amino acids were found to preferentially bind to the mononuclear zinc triflate (1) complex over the corresponding nitrate (2) assembly, with histidine exhibiting a two centre binding mode.     

Steric control over hydrogen bonding in crystalline organic solids: a structural study of N,N'-dialkylthioureas

Hydrogen bonding in crystalline N,N'-dialkylthioureas was examined with the help of single-crystal X-ray diffraction, DFT calculations, and Cambridge Structural Database (CSD) analysis. A CSD survey indicated that unlike the related urea derivatives, which persistently self-assemble into one-dimensional hydrogen-bonded chains, the analogous thioureas can form two different hydrogen-bonding motifs in the solid state: chains, structurally similar with those found in ureas, and dimers, that further associate into hydrogen-bonded layers. The formation of one motif or another can be manipulated by the bulkiness of the organic substituents on the thiourea group, which provides a clear example of steric control over the hydrogen bonding arrangement in crystalline organic solids.     

A preliminary study on fabrication of nanoscale fibrous chitosan membranes in situ by biospecific degradation

A new approach for in situ fabrication of nanoscale fibrous chitosan membrane by biospecific degradation under physiological situation was studied. The chitosan binary blend membranes were fabricated by solvent casting of chitosan solution containing highly deacetylated chitosan (HDC) and moderately deacetylated chitosan (MDC) with different ratio. The biodegradation process was performed in PBS (pH 7.4) containing lysozyme at the temperature of 37 °C. Experimental results from weight loss, reducing sugar in surrounding media, FT-IR, X-ray diffraction, gel permeation chromatography (GPC) and SEM throughout the study showed that the biospecific degradation by lysozyme had removed MDC component selectively. When the ratio of MDC in the binary blend membranes amounted to 0.5, nanoscale domains of HDC and MDC were obtained, and thus a nanoscale fibrous structure was fabricated after biospecific degradation of MDC. This nanofibrous structure and the biospecific degradation of chitosan membranes can have potential advantages and interesting implications in tissue engineering and drug delivery.     

Principles of rapid polymerase chain reactions: mathematical modeling and experimental verification

Polymerase chain reaction (PCR) is an important diagnostic tool for the amplification of DNA. The PCR process can be treated as a problem in biochemical engineering. This study focuses on the development of a mathematical model of the polymerase chain reaction. The PCR process consists of three steps: denaturation of target DNA, annealing of sequence-specific oligonucleotide primers and the enzyme-catalyzed elongation of the annealed complex (primer:DNA:polymerase). The denaturation step separates the double strands of DNA; this model assumes denaturation is complete. The annealing step describes the formation of a primer-fragment complex followed by the attachment of the polymerase to form a ternary complex. This step is complicated by competitive annealing between primers and incomplete fragments including primer-primer reactions. The elongation step is modeled by a stochastic method. Species that compete during the elongation step are deoxynucleotide triphosphates dCTP, dATP, dTTP, dGTP, dUTP, and pyrophosphate. Thermal deamination of dCTP to form dUTP is included in the model. The probability for a species to arrive at the active site is based on its molar fraction. The number of random insertion events depends on the average processing speed of the polymerase and the elongation time of the simulation. The numerical stochastic experiment is repeated a sufficient number of times to construct a probability density distribution (PDF). The moment of the PDF and the annealing step products provide the product distribution at the end of the elongation step. The overall yield is compared to six experimental values of the yield. In all cases the comparisons are very good.