Nanopatterned electrically conductive films of semiconductor nanocrystals

We present the first semiconductor nanocrystal films of nanoscale dimensions that are electrically conductive and crack-free. These films make it possible to study the electrical properties intrinsic to the nanocrystals unimpeded by defects such as cracking and clustering that typically exist in larger-scale films. We find that the electrical conductivity of the nanoscale films is 180 times higher than that of drop-cast, microscopic films made of the same type of nanocrystal. Our technique for forming the nanoscale films is based on electron-beam lithography and a lift-off process. The patterns have dimensions as small as 30 nm and are positioned on a surface with 30 nm precision. The method is flexible in the choice of nanocrystal core-shell materials and ligands. We demonstrate patterns with PbS, PbSe, and CdSe cores and Zn(0.5)Cd(0.5)Se-Zn(0.5)Cd(0.5)S core-shell nanocrystals with a variety of ligands. We achieve unprecedented versatility in integrating semiconductor nanocrystal films into device structures both for studying the intrinsic electrical properties of the nanocrystals and for nanoscale optoelectronic applications.     

UV radiation induces genome-mediated, site-specific cleavage in viral proteins

Much research has been dedicated to understanding the molecular basis of UV damage to biomolecules, yet many questions remain regarding the specific pathways involved. Here we describe a genome-mediated mechanism that causes site-specific virus protein cleavage upon UV irradiation. Bacteriophage MS2 was disinfected with 254 nm UV, and protein damage was characterized with ESI- and MALDI-based FT-ICR, Orbitrap, and TOF mass spectroscopy. Top-down mass spectrometry of the products identified the backbone cleavage site as Cys46-Ser47 in the virus capsid protein, a location of viral genome-protein interaction. The presence of viral RNA was essential to inducing backbone cleavage. The similar bacteriophage GA did not exhibit site-specific protein cleavage. Based on the major protein fragments identified by accurate mass analysis, a cleavage mechanism is proposed by radical formation. The mechanism involves initial oxidation of the Cys46 side chain followed by hydrogen atom abstraction from Ser47 C(α). Computational protein QM/MM studies confirmed the initial steps of the radical mechanism. Collectively, this study describes a rare incidence of genome-induced protein cleavage without the addition of sensitizers.     

TENT4A Non-Canonical Poly(A) Polymerase Regulates DNA-Damage Tolerance via Multiple Pathways That Are Mutated in Endometrial Cancer

TENT4A (PAPD7) is a non-canonical poly(A) polymerase, of which little is known. Here, we show that TENT4A regulates multiple biological pathways and focuses on its multilayer regulation of translesion DNA synthesis (TLS), in which error-prone DNA polymerases bypass unrepaired DNA lesions. We show that TENT4A regulates mRNA stability and/or translation of DNA polymerase η and RAD18 E3 ligase, which guides the polymerase to replication stalling sites and monoubiquitinates PCNA, thereby enabling recruitment of error-prone DNA polymerases to damaged DNA sites. Remarkably, in addition to the effect on RAD18 mRNA stability via controlling its poly(A) tail, TENT4A indirectly regulates RAD18 via the tumor suppressor CYLD and via the long non-coding antisense RNA PAXIP1-AS2, which had no known function. Knocking down the expression of TENT4A or CYLD, or overexpression of PAXIP1-AS2 led each to reduced amounts of the RAD18 protein and DNA polymerase η, leading to reduced TLS, highlighting PAXIP1-AS2 as a new TLS regulator. Bioinformatics analysis revealed that TLS error-prone DNA polymerase genes and their TENT4A-related regulators are frequently mutated in endometrial cancer genomes, suggesting that TLS is dysregulated in this cancer.     

Secretome Analysis of Arabidopsis–Trichoderma atroviride Interaction Unveils New Roles for the Plant Glutamate:Glyoxylate Aminotransferase GGAT1 in Plant Growth Induced by the Fungus and Resistance against Botrytis cinerea

The establishment of plant–fungus mutualistic interaction requires bidirectional molecular crosstalk. Therefore, the analysis of the interacting organisms secretomes would help to understand how such relationships are established. Here, a gel-free shotgun proteomics approach was used to identify the secreted proteins of the plant Arabidopsis thaliana and the mutualistic fungus Trichoderma atroviride during their interaction. A total of 126 proteins of Arabidopsis and 1027 of T. atroviride were identified. Among them, 118 and 780 were differentially modulated, respectively. Bioinformatic analysis unveiled that both organisms’ secretomes were enriched with enzymes. In T. atroviride, glycosidases, aspartic endopeptidases, and dehydrogenases increased in response to Arabidopsis. Additionally, amidases, protein-serine/threonine kinases, and hydro-lyases showed decreased levels. Furthermore, peroxidases, cysteine endopeptidases, and enzymes related to the catabolism of secondary metabolites increased in the plant secretome. In contrast, pathogenesis-related proteins and protease inhibitors decreased in response to the fungus. Notably, the glutamate:glyoxylate aminotransferase GGAT1 was secreted by Arabidopsis during its interaction with T. atroviride. Our study showed that GGAT1 is partially required for plant growth stimulation and on the induction of the plant systemic resistance by T. atroviride. Additionally, GGAT1 seems to participate in the negative regulation of the plant systemic resistance against B. cinerea through a mechanism involving H₂O₂ production.     

Method of Calculation of Stability Constants of Fulvic Complexes on the Example of Copper

On the example of copper fulvate, it is discussed the method of calculation of stability constants of fulvic complexes. At pH = 8, the complex formation of copper（ll） ions with fulvic acids was studied by the solubility method. Fulvic acids were separated from the river Mtkvari by the adsorption-chromotographic method. The charcoal （BAU, Russia） was used as a sorbent. The suspension of copper（If） hydroxide was used as the solid phase, on which was added the increasing quantity of standard solution of fulvic acids. In diluted solutions, at pH = 8 the dominant form of copper（lI） is copper dihydroxo complex Cu（OH）^zO. It was established that in the Cu（OH）2 （solid）-Cu（OH）^20 （solution）-FA^2-H20 system, dominates copper dyhydroxo fulvate complex with the structure 1：1, [Cu（OH）2FA]^2. The average stability constant of copper dyhydroxo fulvate complex was calculated based on experimental data fl [Cu（OH）2FAJ^2 = 4.5× l0^5.     

Fabrication of Nanoporous Alumina Ultrafiltration Membrane with Tunable Pore Size Using Block Copolymer Templates

Control over nanopore size and 3D structure is necessary to advance membrane performance in ubiquitous separation devices. Here, inorganic nanoporous membranes are fabricated by combining the assembly of cylinder‐forming poly(styrene‐block‐methyl methacrylate) (PS‐b‐PMMA) block copolymer and sequential infiltration synthesis (SIS). A key advance relates to the use of PMMA majority block copolymer films and the optimization of thermal annealing temperature and substrate chemistry to achieve through‐film vertical PS cylinders. The resulting morphology allows for direct fabrication of nanoporous AlO_x by selective growth of Al₂O₃ in the PMMA matrix during the SIS process, followed by polymer removal using oxygen plasma. Control over the pore diameter is achieved by varying the number of Al₂O₃ growth cycles, leading to pore size reduction from 21 to 16 nm. 3D characterization, using scanning transmission electron microscopy tomography, reveals that the AlO_x channels are continuous through the film and have a gradual increase in pore size with depth. Finally, the ultrafiltration performance of the fabricated AlO_x membrane for protein separation as a function of protein size and charge is demonstrated.     

A novel co-processing method to manufacture an API for extended release formulation via formation of agglomerates of active ingredient and hydroxypropyl methylcellulose during crystallization

A novel process for generating agglomerates of active pharmaceutical ingredient (API) and polymer by swelling the polymer in a water/organic mixture has been developed to address formulation issues resulting from a water sensitive, high drug load API with poor powder properties. Initially, the API is dissolved in water, following which hydroxypropyl methylcellulose (HPMC) is added, resulting in the imbibing of water, along with the dissolved API, into the HPMC matrix. The addition of acetone and isopropyl acetate (anti-solvents) then causes the API to crystallize inside and on the surface of HPMC agglomerates. The process was scaled up to 20?kg scale. The agglomerates of API and HPMC generated by this process are ～350?µm diameter, robust, and have significantly better flow than the API as measured by Erweka flow testing. These agglomerates exhibit improved bulk density, acceptable chemical stability, and high compressibility. The agglomerates process well through roller compaction and tableting, with no flow or sticking issues. This process is potentially adaptable to other APIs with similar attributes.