A viscometric study of the biodegradation of photographic gelatin by fungi isolated from cinematographic films

The biodegradation of photographic gelatin grade (Bloom 225) material was studied by viscometry in aqueous solution (at 37 °C, 6.67% w/w) using filamentous fungi isolated and identified from cinematographic film stored in different Spanish archives. From viscosity data, different variables such as molecular weight and chain scission were calculated. To ensure initial spore suspension concentration was standardized for all the biodegradation experiments, a correlation between transmittance at 530 nm of fungal spore suspensions and the corresponding cytometric determination of populations was established for all the fungal strains studied in this work. The bioassay experiments were carried out at 25 and 4 °C using an initial concentration of fungi of 4.5×10⁵ conidia/mL except in the case of the genus Alternaria, where the concentration was 10 times lower. The fungal strains were three species of Aspergillus, i.e., A .ustus, A. nidulans var. nidulans, A. versicolor, seven Penicillium chrysogenum strains, and Cladosporium cladosporioides, Alternaria alternata, Mucor racemosus, Phoma glomerata, and Trichoderma longibrachiatum. All were gelatinase positive. Through the viscosity decay profiles with bioassay-time and the corresponding calculated chain scission, the relative quantitative gelatinase efficiency of these fungi has been evaluated.     

Efficiency Enhancement of Organic Solar Cells Using Hydrophobic Antireflective Inverted Moth‐Eye Nanopatterned PDMS Films

Poly‐dimethylsiloxane (PDMS) films with 2D periodic inverted moth‐eye nanopatterns on one surface are implemented as antireflection (AR) layers on a glass substrate for efficient light capture in encapsulated organic solar cells (OSCs). The inverted moth‐eye nanopatterned PDMS (IMN PDMS) films are fabricated by a soft imprint lithographic method using conical subwavelength grating patterns formed by laser interference lithography/dry etching. Their optical characteristics, together with theoretical analysis using rigorous coupled‐wave analysis simulation, and wetting behaviors are investigated. For a period of 380 nm, IMN PDMS films laminated on glass substrates exhibit a hydrophobic surface with a water contact angle (θ_CA) of ≈120° and solar weighted transmittance (SWT) of ≈94.2%, both significantly higher than those (θ_CA≈ 36° and SWT ≈ 90.3%) of bare glass substrates. By employing IMN PDMS films with a period of 380 nm on glass substrates for OSCs, an enhanced power conversion efficiency (PCE) of 6.19% is obtained mainly due to the increased short‐circuit current density (J_sc) of 19.74 mA cm^‐2 compared to the OSCs with the bare glass substrates (PCE = 5.16% and J_sc = 17.25 mA cm^‐2). For the OSCs, the device stability is also studied.     

Chemically functionalized carbon films for single molecule imaging

Many biological complexes are naturally low in abundance and pose a significant challenge to their structural and functional studies. Here we describe a new method that utilizes strong oxidation and chemical linkage to introduce a high density of bioactive ligands onto nanometer-thick carbon films and enable selective enrichment of individual macromolecular complexes at subnanogram levels. The introduced ligands are physically separated. Ni-NTA, Protein G and DNA/RNA oligonucleotides were covalently linked to the carbon surface. They embody negligible mass and their stability makes the functionalized films able to survive long-term storage and tolerate variations in pH, temperature, salts, detergents, and solvents. We demonstrated the application of the new method to the electron microscopic imaging of the substrate-bound C3PO, an RNA-processing enzyme important for the RNA interference pathway. On the ssRNA-linked carbon surface, the formation of C3PO oligomers at subnanomolar concentrations likely mimics their assembly onto ssRNA substrates presented by their native partners. Interestingly, the 3D reconstructions by negative stain EM reveal a side port in the C3PO/ssRNA complex, and the 15 Å cryoEM map showed extra density right above the side port, which probably represents the ssRNA. These results suggest a new way for ssRNAs to interact with the active sites of the complex. Together our data demonstrate that the surface-engineered carbon films are suitable for selectively enriching low-abundance biological complexes at nanomolar level and for developing novel applications on a large number of surface-presented molecules.     

Solvation Force and Confinement-Induced Phase Transitions of Model Ultra Thin Films

Abstract

The static (equilibrium) properties of atomically thin films confined between two surfaces are studied as a function of surface separation by Grand Canonical Monte Carlo and Molecular Dynamics simulations. A model was used, in which the fluid and wall species consist of two different Lennard-Jones rare gas atoms. This was designed to mimic the static SFA experiments in which it is known that epitaxy is not necessary for inducing an oscillatory solvation force in simple non polar liquids. We have been able to simulate, using this simple system, many aspects of the equilibrium properties observed in the experiments. The solvation force is an exponentially damped, periodic curve. All peaks of maximum amplitude in the solvation force correspond to solid-like structures. These structures melt in increasing the surface separation. A further increase in separation leads to the addition of a whole layer and the recrystallisation of the film. In addition this model displays an interesting phenomenon of confinement induced solid-solid phase transition. Two different stable packing (bcc and triclinic) can be observed in the bilayer film and a transition from one to the other occurs when the surface separation is changed. This phase change has been studied as a function of pressure and temperature. As compared to the simulations using a ‘commensurate’ model, in which the fluid and wall species are made of like atoms, the results obtained here are in much better agreement with experimental findings.     

Ordered Water Structure and Enhanced Reactivity

Analogies are drawn between the ordered structure of the colloidal water pool of reversed micelles, water present in the micropores of dense cellulose acetate films and the water vicinal to interfaces in biological systems. Chemical reactivity is enhanced in the solvent which is entirely different from normal water. In particular, it is possible to use the stretched water present in the cellulose acetate films to synthesise biochemicals.