Mccannsanders0708

This was rationalized by dichroic ratios of the amide I component at 1696 cm-1 assigned to the (0, π) mode of antiparallel β-sheet structures, whose transition dipole moment M is located in parallel to both β-sheet plane and chain direction. The calculated high molecular order parameter S ≈ 0.40 suggested vertically (out-of-plane) oriented antiparallel β-sheet stacks with tilt angles of γ ≈ 39° to the surface normal. Microscale (thick) films, in contrast, revealed low order parameters S ≈ 0. Scanning force microscopy on thin eADF4 films at silicon substrates showed dewetted polymer film structures rather at the micro-scale. These findings give new insights in the role of the β-sheet crystallite orientation for the mechanical properties of spider silk materials.Readily available, low-cost 4R-hydroxy-l-proline (Hyp) is introduced as a "doubly customizable" unit for the generation of libraries of structurally diverse compounds. Hyp can be cleaved at two points, followed by the introduction of new functionalities. In the first cycle, the removal and replacement of the carboxylic group are carried out, followed (second cycle) by the scission of the 4,5-position and manipulation of the resulting chains. In this way, three new chains are generated and can be transformed independently to afford a diversity of products with tailored substituents, such as β-amino aldehydes, diamines, β-amino acid derivatives, including N-alkylated ones, or modified peptides. Many of these products are high-profit compounds but, in spite of their commercial value, are still scarce. Moreover, the process takes place with stereochemical control, and either pure R or S isomers can be obtained with small variations of the synthetic route.An efficient protocol for the asymmetric hydroarylation and hydroalkenylation of benzo[b]thiophene 1,1-dioxides with organoboranes has been developed. The combination of a rhodium(I) precatalyst and a chiral diene ligand constitutes the catalytic system, which enables the facile synthesis of 2,3-dihydrobenzo[b]thiophene 1,1-dioxides in good yields with high enantioselectivities. The merging of this asymmetric hydroarylation with the downstream alkylations delivers 2,3-dihydrobenzo[b]thiophene 1,1-dioxides that contain two continuous quaternary stereocenters with high enantioselectivities in a diastereodivergent manner.Acinetobacter baumannii has emerged as a major bacterial pathogen during the past three decades. learn more The majority of the A. baumannii infections occur in hospitals and are caused by strains endowed with high desiccation tolerance, which represents an essential feature for the adaptation to the nosocomial environment. This work aims at investigating the desiccation response of the multidrug-resistant A. baumannii strain ACICU as a function of the bacterial growth phase and oxygen availability, by correlating bacterial survival with shape alterations. The three-dimensional morphological analysis of bacteria was carried out by atomic force microscopy (AFM), following the evolution of bacterial shape descriptors, such as the area, volume, roughness of individual cell membranes, and the cell cluster roughness, which exhibited peculiar and distinctive behavior as a function of the growth conditions. AFM images of A. baumannii ACICU cells revealed the prevalence of the coccoid morphology at all growth stages, with a tendency to reduce their size in the stationary phase, accompanied by a higher survival rate to air-drying. Moreover, cells harvested from the logarithmic phase featured a larger volume and resulted to be more sensitive to desiccation compared to the cells harvested at later growth stages. In addition, oxygen deprivation caused a significant decrease in cellular size and was associated with the formation of pores in the cell membrane, accompanied by a relative reduction in culturability after desiccation. Morphological plasticity and multidrug resistance may contribute to desiccation tolerance and therefore to persistence in the hospital setting.A series of side-chain thioether-linked OEGylated poly(glutamic acid) (PGAs) have been synthesized by "thiol-ene" synthetic methodology, where both the oligo-ethylene glycol (OEG) length and the hydrophobic linkers at the side chains are varied to learn how these structural features affect the secondary structure and thermoresponsive behaviors in water. Before side-chain oxidation, the structural factors affecting the α-helicity include the backbone length, the OEG length, and the hydrophobic linkers' length at the side chains; however, the OEG length plays the most crucial role among these factors because longer OEG around the peripheral side chains can stop water penetration into the backbone to disturb the intramolecular H bonds, which finally allows stabilizing the α-helix; after the oxidation, the polypeptides show increased α-helicity because of the enhanced hydrophilicity. More interestingly, a rare oxidation-induced conformation transition from the ordered β-sheet to the ordered α-helix can be achieved. In addition, only the OEGylated poly(glutamic acids) (PGAs) with shorter hydrophobic linkers and longer OEG can display the thermoresponsive properties before the oxidation but the subsequent oxidation can cause the polypeptides bearing longer hydrophobic linkers to exhibit the thermosensitivity since sulfone formation at the side chain can lead to final hydrophilicity-hydrophobicity balance. This work is meaningful to understand the secondary structure-associated solution behaviors of the synthetic polypeptides.An N-heterocyclic carbene (NHC)-catalyzed strategy has been developed to address the issue of using toxic transitional metals in the field of C-C bond activation. The novel reaction mode enables an efficient docking between the cyanoalkyl from the cycloketone oxime derivative and the acyl group from the aldehyde, affording ketonitrile in moderate to good yields, which is one kind of useful building block for synthesizing nitrogen-containing pharmacophores.A rapid and simple analytical approach is developed to screen the semiconducting properties of metal organic frameworks (MOFs) by modeling the band structure and predicting the density of state of isoreticular MOFs (IRMOFs). One can consider the periodic arrangement of metal nodes linked by organic subunits as a 1D periodic array crystal model, which can be aligned with any unit-cell axis included in the IRMOF's primitive cubic lattice. In such a structure, each valence electron of a metal atom feels the potential field of the entire periodic array. We allocate the 1D periodic array in a crystal unit cell to three IRMOFs-n (n = 1, 8, and 10) of the Zn4O(L)3 IRMOF series and apply the model to their crystal lattices with unit-cell constants a = 25.66, 30.09, and 34.28 Å, respectively. By solving Schrödinger's equation with a Kronig-Penney periodic potential and fitting the computed energy spectra to IRMOFs' experimental spectroscopic data, we model electronic band structures and obtain densities of state. The band diagram of each IRMOF reveals the nature of its electronic structures and density of state, allowing one to identify its n- or p-type semiconducting behavior.