Size-modulated synergy of cellulase clustering for enhanced cellulose hydrolysis

Immobilization of enzymes onto nanoparticles for enhanced biocatalytic activity via enzyme clustering is a growing field. In this paper, the effect of nanoparticle size on the hydrolytic activity of artificial cellulosomes was investigated. A simple method based on metal affinity coordination was employed to directly conjugate two enzymes, an endoglucanase CelA and an exoglucanase CelE, onto CdSe–ZnS core–shell quantum dots (QDs) without the use of any chemical modification or linker molecules such as streptavidin. Artificial cellulosomes were created by clustering the enzymes onto two different QDs (5 and 10 nm) to systematically study the influence of particle size and QD to enzyme ratio on the enhancement in cellulose hydrolysis. Our results indicate that enzyme proximity is the most important factor for activity enhancement while the influence of particle size is relatively modest. This detailed understanding will provide insights for the design of other artificial cellulosomes based on nanoclustering of multiple catalytic domains with significantly enhanced activities, and may be applicable for designing improved nanobiocatalysts for biofuel production, bioremediation, and drug design.     

In Vivo Quantitative Assessment of Myocardial Structure,Function, Perfusion and Viability Using Cardiac Micro-computed Tomography

The use of Micro-Computed Tomography (MicroCT) for in vivo studies of small animals as models of human disease has risen tremendously due to the fact that MicroCT provides quantitative high-resolution three-dimensional (3D) anatomical data non-destructively and longitudinally. Most importantly, with the development of a novel preclinical iodinated contrast agent called eXIA160, functional and metabolic assessment of the heart became possible. However, prior to the advent of commercial MicroCT scanners equipped with X-ray flat-panel detector technology and easy-to-use cardio-respiratory gating, preclinical studies of cardiovascular disease (CVD) in small animals required a MicroCT technologist with advanced skills, and thus were impractical for widespread implementation. The goal of this work is to provide a practical guide to the use of the high-speed Quantum FX MicroCT system for comprehensive determination of myocardial global and regional function along with assessment of myocardial perfusion, metabolism and viability in healthy mice and in a cardiac ischemia mouse model induced by permanent occlusion of the left anterior descending coronary artery (LAD).     

Suppressing Interfacial Dipoles to Minimize Open‐Circuit Voltage Loss in Quantum Dot Photovoltaics

Quantum‐dot (QD) photovoltaics (PVs) offer promise as energy‐conversion devices; however, their open‐circuit‐voltage (V_OC) deficit is excessively large. Previous work has identified factors related to the QD active layer that contribute to V_OC loss, including sub‐bandgap trap states and polydispersity in QD films. This work focuses instead on layer interfaces, and reveals a critical source of V_OC loss: electron leakage at the QD/hole‐transport layer (HTL) interface. Although large‐bandgap organic materials in HTL are potentially suited to minimizing leakage current, dipoles that form at an organic/metal interface impede control over optimal band alignments. To overcome the challenge, a bilayer HTL configuration, which consists of semiconducting alpha‐sexithiophene (α‐6T) and metallic poly(3,4‐ethylenedioxythiphene) polystyrene sulfonate (PEDOT:PSS), is introduced. The introduction of the PEDOT:PSS layer between α‐6T and Au electrode suppresses the formation of undesired interfacial dipoles and a Schottky barrier for holes, and the bilayer HTL provides a high electron barrier of 1.35 eV. Using bilayer HTLs enhances the V_OC by 74 mV without compromising the J_SC compared to conventional MoO₃ control devices, leading to a best power conversion efficiency of 9.2% (>40% improvement relative to relevant controls). Wider applicability of the bilayer strategy is demonstrated by a similar structure based on shallow lowest‐unoccupied‐molecular‐orbital (LUMO) levels.     

Two new antibacterial sesquiterpenoids from Centipeda minima

Two new guaiane-type sesquiterpene lactones, compounds 1 and 2, along with three known guaianolide- or pseudoguaianolides, were isolated from Centipeda minima (whole plant). Their structures were identified by spectroscopic and mass-spectrometric analyses. The configuration at C5 of the guaiane framework of 1 was rationalized by quantum-mechanical calculations (Table 2). All compounds were found to be active against eight different microbial pathogens (Table 3), with MIC values in the range of 6.25-100 microg/ml.     

Evaluation of C-H cdots,three dots,centered O hydrogen bonds in native and misfolded proteins

Non-traditional C-H cdots, three dots, centered Y hydrogen bonds, in which a carbon atom acts as the hydrogen donor and an electronegative atom Y (Y=N, O or S) acts as the acceptor, have been reported in proteins, but their importance in protein structures is not well established. Here, we present the results of three computational tests that examine the significance of C-H cdots, three dots, centered Y bonds involving the C(alpha) in proteins. First, we compared the number of C(alpha)-H cdots, three dots, centered Y bonds in native structures with two sets of compact, energy-minimized decoy structures. The decoy structures contain about as many C(alpha)-H cdots, three dots, centered Y bonds as the native structures, indicating that the constraints of chain connectivity and compactness can lead to incidental formation of C(alpha)-H cdots, three dots, centered Y bonds. Secondly, we examined whether short C(alpha)-H cdots, three dots, centered Y bonds have a tendency to be linear, as is expected for a cohesive hydrogen-bonding interaction. The native structures do show this trend, but so does one of the decoy sets, suggesting that this criterion is also not sufficient to indicate a stabilizing interaction. Finally, we examined the preference for C(alpha)-H cdots, three dots, centered Y bond donors to be near to strong hydrogen bond acceptors. In the native proteins, the alpha protons attract strong acceptors like oxygen atoms more than weak acceptors. In contrast, hydrogen bond donors in the decoy structures do not distinguish between strong and weak acceptors. Thus, any individual C(alpha)-H cdots, three dots, centered Y bond may be fortuitous and occur due to the polypeptide connectivity and compactness. Taken collectively, however, C(alpha)-H cdots, three dots, centered Y bonds provide a weakly cohesive force that stabilizes proteins.     

Unity of measurement and motion

Issues addressed in H.H. Pattee's origin of life laboratory in the 1960s and their connection to the physics–evolution–language problematic are indicated. The problem of quantum measurement played a central role. The problem is herein examined in the light of the fluctuon model; in particular, as the model applies to gravity. The main conclusion is that measurement and motion are a unitary process. All accelerations are accompanied by a cycle involving the annihilation and creation of superpositions. Gravitational collapse is also a cyclic process in the fluctuon model. By a suitable transformation, it can be seen that interactions underlying superpositional collapse are the same as those operative in gravitational collapse. Implications for the origin of cellular life and the development of symbolic systems are considered.     

体内光量子点可视化图像在脑肿瘤中的应用

恶性胶质瘤年发病率约为5/100,000。美国每年有超过14,000例的新发恶性脑胶质瘤患者。治疗主要以手术治疗为主,手术肿瘤的切除程度影响患者的预后。外科手术治疗脑肿瘤需要精确定位脑肿瘤组织在正常脑组织中的位置以便能够获得精确的组织活检和肿瘤的完全切除。量子点是稳定存在的,产生荧光的可视化半导体纳米晶体。静脉注射量子点伴随着网状内皮系统和巨噬细胞的隔离。巨噬细胞可渗入到肿瘤组织并且能够吞噬通过静脉注射的光量子来产生可视化的肿瘤标记。通过巨噬细胞介导,将光量子运输至肿瘤组织展现了一种新兴技术来标记术前肿瘤组织。由于肿瘤组织中的光量子可以被光学成像和光谱学工具来探测,因此在脑肿瘤组织活检和切除中可以为外科医生提供可视化得实时反馈。     

Effects of palmitoylation on the diffusional movement of BKCa channels in live cells

BK_Ca channels are palmitoylated at a cluster of cysteine residues within the cytosolic linker connecting the 1st and 2nd transmembrane domains, and this lipid modification affects their surface expression. To verify the effects of palmitoylation on the diffusional dynamics of BK_Ca channels, we investigated their lateral movement. Compared to wild-type channels, the movement of mutant palmitoylation-deficient channels was much less confined and close to random. The diffusion of the mutant channel was also much faster than that of the wild type. Thus, the lateral movement of BK_Ca channels is greatly influenced by palmitoylation.     

Bio-inspired photoresponse of porphyrin-attached gold nanoparticles on a field-effect transistor

A bio-inspired photoresponse was engineered in porphyrin-attached Au nanoparticles (AuNPs) on a field-effect transistor (FET). The system mimics photosynthetic electron transfer, using porphyrin derivatives as photosensitizers and AuNPs as photoelectron counting devices. Porphyrin-protected AuNPs were immobilized onto the gate of an FET via the formation of self-assembled monolayers. Photoinduced electron transfer from the porphyrin led to single electron transfer at the Au nanoparticles, which was monitored via a changing gate voltage on the FET in the presence of organic electrolyte. The further attachment of other functional molecules to this system should enable various other potential functionalities. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: Keys to Produce Clean Energy.