Conjugates of amino acids with glucosamine isolated from the plasma of rats with Guerin carcinoma

The conjugate of amino acids and glucosamine (glycamine) was purified to homogeneity from blood plasma of rats with Guerin carcinoma. The NH2-groups of amino acids in the glycamine are free. Amino acids are linked to glucosamine via carboxyl groups. 8 amino acids residues were identified in the glycamine molecule (Glu-2, Ser-2, Gly-3, Lys-1). Spatial atomic-molecular model of the glycamine molecule was developed. Two glucosamine molecules are linked to diaminosaccharide via (1-4)-bond, 8 amino acid molecules are linked to diaminosaccharide via 6 ester and 2 pseudopeptide bonds.     

Design Principle of Conjugated Polyelectrolytes to Make Them Water‐Soluble and Highly Emissive

The correlation between the molecular design of a conjugated polyelectrolyte (CPE) and its aggregated structure and the emissive properties in water is systematically investigated by means of UV–vis spectrometry, fluorescence spectroscopy, and scanning/transmission electron microscopy. Five different and rationally designed CPEs having carboxylic acid side chains are synthesized. All five conjugated polyelectrolytes are seemingly completely soluble in water in visual observation. However, their quantum yields are dramatically different, changing from 0.45 to 51.4%. Morphological analysis by electron microscopy combined with fluorescence spectrophotometry reveals that the CPEs form self‐assembled aggregates at the nanoscale depending on the nature of their side chains. The feature of the self‐assembled aggregates directly determines the emissive property of the CPEs. The nature and the length of the spacer between the carboxylic acid group and the CPE backbone have a strong influence on the quantum yield of the CPEs. Our study demonstrates that bulky and hydrophilic side chains and spacers are required to achieve complete water‐solubility and high quantum yield of CPEs in water, providing an important molecular design principle to develop functional CPEs.     

Molecular roughness analysis of developed resist by LER method

In this paper, line edge roughness (LER) analysis on top–down images acquired by means of a scanning electron microscope is here proposed as a powerful and non-invasive technique to map the molecular aggregate distribution in a chemically amplified resist: in particular the periodicity of the aggregates themselves is determined via power spectral density method (PSD). The roughness of two resist developers with different chemical composition will be compared on the base of 1D power spectral density function: in case of SEM acquisition, the profile to be analyzed is extracted from a top–down acquisition, while atomic force microscope (AFM) inspection of surface topography allows to calculate PSD along a user-defined line. The two approaches confirm a reduced surface roughness in case of development with smaller molecule.     

Proton‐Conducting Aromatic Polymers Carrying Hypersulfonated Side Chains for Fuel Cell Applications

Polysulfone main chains have been functionalized with hypersulfonated aromatic side chains where the sulfonic acid groups were highly concentrated on a local scale, with two acid groups placed on the same aromatic ring. This molecular design was implemented to promote the nanophase separation that takes place in proton‐exchange membranes between the hydrophobic polymer main chain and the hydrophilic ionic groups responsible for the water uptake and conduction. Morphological investigations revealed that polysulfones functionalized with disulfonaphthoxybenzoyl or trisulfopyrenoxybenzoyl side chains contained larger and more uniform ionic clusters, as compared to conventionally sulfonated polysulfones where the acid groups are dispersed along the main chain. Membranes based on the polymers carrying hypersulfonated side chains formed efficient networks of water‐filled nanopores upon hydration, which facilitated excellent levels of proton conductivity exceeding that of the commercial Nafion membrane at moderate water uptakes.     

Modulation of the spin transport properties of the iron-phthalocyanine molecular junction by carbon chains with different connection sites

Based on the non-equilibrium Green's function method combined with the density functional theory, the spin transport properties of an iron-phthalocyanine (FePc) molecule connected to two Au electrodes by carbon chains are investigated, and three kinds of connecting position between FePc molecule and carbon chains are considered. It is found that the spin filtering effect and the negative differential resistance (NDR) behavior in these systems can be achieved in the calculated bias region. However, the efficiency and the bias region of spin filtering are affected significantly by the connecting positions. The above results are explained by the spin-resolved transmission spectrum, electron transmitting path, molecular projected self consistent Hamiltonian state, and the local density of states (LDOS) analyses. Our calculations demonstrate a promising modification for developing molecule spintronic devices.     

氨基酸影响草酸钙成核和生长的SEM和XRD研究

应用扫描电子显微镜(SEM)和X射线衍射仪(XRD)研究了不同种类氨基酸对尿结石主要成分一水草酸钙(COM)晶体生长的影响,这些氨基酸分别为酸性氨基酸谷氨酸、天冬氨酸、中性氨基酸苯丙氨酸及碱性氨基酸组氨酸.结果表明:氨基酸主要通过静电作用影响草酸钙的结晶.酸性氨基酸在抑制COM成核的同时促进其生长;碱性的组氨酸在0.01 mmol/L～0.1 mmol/L浓度区间内抑制成核,而在0.1 mmol/L～1.0 mmol/L区间则促进COM成核;中性的苯丙氨酸在0.01 mmol/L～0.1 mmol/L区间抑制COM的生长,而在0.1 mmol/L～1.0 mmol/L区间抑制COM的成核.研究氨基酸对含钙尿石晶体生长的影响,对探索氨基酸及富含酸性氨基酸残基的蛋白质在尿石形成过程中的作用及合成肽在尿石治疗的潜在应用方面有重要意义.     

Impact of the Nature of the Side‐Chains on the Polymer‐Fullerene Packing in the Mixed Regions of Bulk Heterojunction Solar Cells

Polymer‐fullerene packing in mixed regions of a bulk heterojunction solar cell is expected to play a major role in exciton‐dissociation, charge‐separation, and charge‐recombination processes. Here, molecular dynamics simulations are combined with density functional theory calculations to examine the impact of nature and location of polymer side‐chains on the polymer‐fullerene packing in mixed regions. The focus is on poly‐benzo[1,2‐b:4,5‐b′]dithiophene‐thieno[3,4‐c]pyrrole‐4,6‐dione (PBDTTPD) as electron‐donating material and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as electron‐accepting material. Three polymer side‐chain patterns are considered: i) linear side‐chains on both benzodithiophene (BDT) and thienopyrroledione (TPD) moieties; ii) two linear side‐chains on BDT and a branched side‐chain on TPD; and iii) two branched side‐chains on BDT and a linear side‐chain on TPD. Increasing the number of branched side‐chains is found to decrease the polymer packing density and thereby to enhance PBDTTPD–PC₆₁ BM mixing. The nature and location of side‐chains are found to play a determining role in the probability of finding PC₆₁BM molecules close to either BDT or TPD. The electronic couplings relevant for the exciton‐dissociation and charge‐recombination processes are also evaluated. Overall, the findings are consistent with the experimental evolution of the PBDTTPD–PC₆₁BM solar‐cell performance as a function of side‐chain patterns.     

INVESTIGATION OF PROPERTIES OF INFRARED ABSORPTION OF α-HELIX PROTEIN MOLECULES

The mechanism and properties of infrared absorption of α-helix protein molecules are studied by a theory of bio-energy transport established on the basis of molecular structure. From the vibrational energy-spectra of molecules obtained from this theory we know that the infrared lights with wavelengths of 2 µm ?7 µm can be absorbed by α-helix protein molecules. This is basically consistent with experimental data of infrared absorption of collagen and hemoglobin and bivine serum albumen (BSA) proteins with α-helix structure. From these results we account further for the mechanism and properties of biological effect of infrared lights absorbed by the living systems, i.e., the energy of infrared lights is directly absorbed by the amide-Is in amino acid residues in the protein molecules, which results in vibration of amide-1 and change of conformation of proteins and transport of bio-energy from one place to other along the protein molecular chains in human beings and animals. This is a kind of non-thermally biological effect.     

Correlations between amino acid hydrophobicity scales and stain exclusion capacity of type 1 collagen fibrils

The relationship between the negative staining band pattern of type 1 native collagen fibrils and the amino acid distribution along the fibril axis was studied by comparing averaged microdensitograms with theoretical traces calculated on the basis of different amino acid parameters. As well as the spatial parameter "bulkiness" (volume/length, ratio), various literature-reported scales of "hydrophobicity" were tested. Two "hydrophobicity" sets allowed a better fit with the actual patterns than "bulkiness" values. However, a general improvement in simulations was achieved by associating most "hydrophobicity" sets with the "bulkiness" set. These results suggest that amino acid "hydrophobicity" plays a key role in the appearance of negative staining patterns but a composite mechanism would seem to occur: the accessibility of available intermolecular interstices may be conditioned by molecular hindrance, corresponding to amino acid "bulkiness" as well as by water-repulsion effect, which correlates with amino acid "hydrophobicity." Moreover, a detailed comparison of actual and simulated patterns suggests that a modulation exists in the effectiveness of these two factors along each D-period according to the different molecular packing and concentration of hydrophobic amino acid clusters within overlap regions and gap regions, respectively.     

Hydrogel Scaffolds of Amphiphilic and Acidic β‐Sheet Peptides

Amphiphilic and acidic β‐sheet‐forming peptides (AAβPs) having the sequence Pro‐Y‐(Z‐Y)₅‐Pro, Y = Glu or Asp and Z = Phe or Leu may assemble into hydrogel structures at near neutral pH values, several units higher than the intrinsic pKa of their acidic amino acid side chains. The bottom‐to‐top design strategy enables the rationally supported association between the peptides' amino acids composition and bulk pH hydrogelation. Hydrogen bonds between the acidic amino acids side chains in the β‐sheet structure are found to contribute substantially to the stabilization of AAβPs hydrogels. The negatively charged peptides are also found to form gels at lower concentration in presence of calcium ions. Bone forming cells may be cultured on two‐dimensional films of AAβPs hydrogels that form at physiological pH values as well as within three dimensional hydrogel matrices. These acidic‐rich peptides hydrogels may become advantageous in applications related to engineering of mineralized tissues providing controllable, multifunctional calcified scaffolds to affect both the biological activity and the inorganic mineralization.     

取代位置对香豆素衍生物二阶非线性光学性质影响的DFT研究

采用密度泛函理论（DFT）B3LYP/6-31G方法,对设计的6个不同位置取代氨基的香豆素衍生物的几何构型进行优化。在所得优化结构的基础上对这些分子的稳态二阶NLO系数β值进行计算分析,并采用含时密度泛函理论（TD-DFT）方法计算了其电子性质,研究了取代位置对香豆素类衍生物分子的二阶NLO性质的影响规律。结果表明：当氨基取代在4号位时香豆素分子中的羰基表现出供电性,对分子内电荷转移非常不利,不利于提高分子的β值;当氨基取代在在3、5、6、7、8位时分子中的羰基表现出吸电性,使分子形成D-π-A构型,并且氨基在3、7位的取代能够扩大体系的共轭范围,有效增加了香豆素分子的βtot值。     

Intrinsic electrochemical doping in blue light emitting polymer devices utilizing a water soluble anionic conjugated polymer

We report on light emitting device related properties of the water soluble blue light emitting anionic poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} copolymer (PBS-PFP) with alkyl sulfonic acid sodium side chains. Compared to organic solvents water has the advantage of being environmentally friendly, which simplifies the handling during device fabrication by novel preparation techniques such as ink-jet printing. Light emitting devices fabricated from this polymer in thin film configuration show stable blue emission with an emission maximum at approximately 420 nm. Investigations concerning the current–density/voltage and the luminance/voltage device characteristics as well as the current–density over operation time at constant biases allow the identification of intrinsic electrochemical doping effects caused by ionic groups attached on the side chains of the polymer. Due to this fact, firstly the electroluminescence onset voltage for devices using high work-function electrodes for electron injection such as aluminum, which has the advantage of being air stable, can be distinctly reduced, and secondly devices fabricated from this polymer showed luminance in forward bias direction as well as in reverse bias direction.     

Bioinspired Magnetite Crystallization Directed by Random Copolypeptides

Control over magnetite (Fe₃O₄) formation is difficult to achieve in synthetic systems without using non‐aqueous media and high temperatures. In contrast, Nature employs often intrinsically disordered proteins to tightly tailor the size, shape, purity, and organization of the nanocrystals to optimize their magnetic properties. Inspired by such “flexible polyelectrolytes,” here random copolypeptides having different amino acid compositions are used as control agents in the bioinspired coprecipitation of magnetite through a ferrihydrite precursor, following a recently developed mineralization protocol. Importantly, the copolypeptide library is designed such that the amino acid composition can be optimized to simultaneously direct the size of the nanoparticles as well as their dispersibility in aqueous media in a one‐pot manner. Acidic amino acids are demonstrated to regulate the crystal size by delaying nucleation and reducing growth. Their relative content thus can be balanced to tune between the superparamagnetic and ferrimagnetic regimes, and high contents of negatively charged amino acids result in colloidal stabilization of superparamagnetic nanoparticles at high pH. Conversely, with positively charged lysine‐rich copolypeptides ferrimagnetic crystals are obtained which are stabilized at neutral pH and self‐organize in chains, as visualized by cryo‐transmission electron microscopy. Altogether, the presented findings give important insights for the future development of additive‐mediated nanomaterial syntheses.     

Correlation Between Molecular Structure,Microscopic Morphology,and Optical Propertiesof Poly(tetraalkylindenofluorene)s

The emission properties of polyindenofluorenes with various proportions of straight‐ and branched‐chain alkyl substituents have been compared. The polymer with straight octyl substituents shows green emission due to formation of aggregates, while the polymer with branched 2‐ethylhexyl substituents shows blue emission. Studies of the film morphology show the presence of ordered structures due to π‐stacking of the polymer chains for the octyl‐substituted polymer, whereas the polymer with branched side‐chains shows no such order. Copolymers show intermediate behavior. A clear correlation is established between the degree of straight‐chain alkyl substitution, the formation of ordered structures in the films, and the amount of long wavelength emission in the solid‐state spectra.     

Scanning mutagenesis studies of the M1 muscarinic acetylcholine receptor

Following the solution of the structure of bovine rhodopsin by X-ray crystallography, it has been possible to build an improved homology model of the M(1) muscarinic acetylcholine receptor. This has been used to interpret the outcome of an extensive series of scanning and point mutagenesis studies on the transmembrane domain of the receptor. Potential intramolecular interactions enhancing the stability of the protein fold have been identified. The residues contributing to the binding site for the antagonist, N-methylscopolamine, and the agonist, acetylcholine have been mapped. The positively charged headgroups of these ligands appear to bind in a charge-stabilized aromatic cage formed by amino acid side chains in transmembrane (TM) helices 3, 6, and 7, while residues in TM 4 may participate in a peripheral docking site. Closure of the cage around the headgroup of acetylcholine may help to transduce binding energy into receptor activation, possibly disrupting a set of Van der Waals interactions between a set of residues underlying the binding site which help to constrain the receptor to the inactive state, in the absence of agonist. This may trigger the reorganization of a hydrogen bonding network between highly conserved residues in the core of the receptor, whose integrity is crucial for activation.     

Impact of Polystyrene Oligomer Side Chains on Naphthalene Diimide–Bithiophene Polymers as n‐Type Semiconductors for Organic Field‐Effect Transistors

A series of naphthalene diimide‐based conjugated polymers are prepared with various molar percentage of low molecular weight polystyrene (PS) oligomer of narrow polydispersity as the side chain. The PS side chains are incorporated through preparation of a macromonomer by chain termination of living anionic polymerization. The effects of the PS side chains amount (0–20 mol%) versus overall sidechain on the electrical properties of the resulting polymers as n‐type polymer semiconductors in field‐effect transistors are investigated. We observe that all the studied polymers show similarly high electron mobility (≈0.2 cm² V^?1 s^?1). Importantly, the polymers with high PS side chain content (20 mol%) show a significantly improved device stability under ambient conditions, when compared to the polymers at lower PS content (0–10 mol%). By comparing this observation to the physical blending of the conjugated polymer with PS, we attribute the improved stability to the covalently attached PS side chains potentially serving as a molecular encapsulating layer around the conjugated polymer backbone, rendering it less susceptible to electron traps such as oxygen and water molecules.     

(CdSe)1/(ZnSe)1应力半导体材料缺陷能级

用实空间 Recursion方法计算 (Cd Se) 1 / (Zn Se) 1 应力半导体材料的总态密度、局域态密度、分波态密度 ,研究了局域特性和缺陷能级 ,得出了一些有价值的结论。     

A Theoretical Study of Substitution Effects in Unimolecular Rectifiers

The concept of molecular rectifiers introduced by Aviram and Ratner in 1974 has been the starting point of the field of molecular electronics and the possibility of unimolecular rectification has been widely debated ever since. Despite the large amount of publications on this topic over the years, the physical mechanisms leading to this phenomenon have not yet been clarified to the point where a systematic route for enhancing the rectification ratio (RR) of molecules could be suggested. We present here a theoretical study of RR for a range of molecules with a carboxylic group as a bridge between π‐conjugated chains substituted by nitro and amino groups to improve the rectification. We estimate the RR in two distinct ways, namely: i) as the ratio of the threshold electric fields required to transfer one electron between the donor and acceptor units of the molecule and vice versa, using quantum‐chemical calculations based on the semi‐empirical Hartree–Fock Austin Model 1 (AM1) method, ii) as the ratio of the currents in forward versus reverse bias, as obtained with a non‐equilibrium Green's function (NEGF) approach for charge transport through gold/molecule/gold junctions within the framework of density functional theory (DFT). The trends in RR as a function of the molecular structure agree very well when these two methods are compared and can be explained in terms of the relative position of the nitro group within the generated electrostatic potential. These findings allow us to derive some general conclusions about the physical mechanisms behind unimolecular rectification.     

Analysis of photoreceptor membrane turnover in a Drosophila visual mutant, rdgA, by electron microscope autoradiography

A Drosophila visual mutant, rdgA, has photoreceptor cells whose rhabdomeres degenerate in several days after eclosion. Incorporations of 3H-amino acids, and 3H-mannose and 3H-glucosamine residues into the photoreceptive membranes were studied in newly emerged rdgA mutant flies by electron microscope autoradiography. The amount of 3H-amino acids incorporated in rdgA rhabdomeres at 3 hr after the injection was about 50%, and that of 3H-sugar residues was about 20% of normal. Together with our previous finding that degradative activity is low in rdgA cell bodies at this time, these data indicate that the supply of photoreceptive membrane proteins is defective in rdgA.     

2D Chiroptical Nanostructures for High‐Performance Photooxidants

Modulation of the chirality of solid‐like nanoscale membranous structures used as selective photooxidants is an important goal of chemical and materials science. Here, the fabrication of a chiral plasmonic nanoparticle monolayer film which is a highly selective photooxidant under circularly polarized light (CPL) in the visible‐light region is reported. The chiroptical activity of the film can be controlled by altering the amount and stereochemistry of amino acids. The experiments disclose that this stable and reusable catalyst is active in the selective oxidation of glucose enantiomers and CPL of opposite polarization gives around 10.3‐fold increase in conversion rates. The results reveal that the handedness of polarized light dominates the catalytic activity of the chiral film. It is demonstrated that the specific chiral binding of the amino acid ligands and the local field enhancement in the light‐limited regime regulates the selective photocatalytic performance, as confirmed by first‐principles density functional theory and physical field simulations. With the catalyst's signature ability for chiral recognition and switching of handedness of polarized light, the discovery provides a foundation for designing and tailoring chiral inorganic photooxidants. This research also sets an example for the development of light–matter interactions and polarized optics.