Amphiphilic water soluble cationic ring opening metathesis copolymer as an antibacterial agent

Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC ₅₀ = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer.     

Effects of OCRA parameters and learning rate on machine scheduling

Central European Journal of Operations Research - In this paper, the effects of Occupational Repetitive Actions (OCRA) parameters, learning rate on process times, and machine scheduling were...     

Contact 3-manifolds with infinitely many Stein fillings

Infinitely many contact 3-manifolds each admitting infinitely many pairwise non-diffeomorphic Stein fillings are constructed. We use Lefschetz fibrations in our constructions and compute their first homologies to distinguish the fillings.

     

Antiferromagnetic Coupling in a New Mn(III) Schiff Base Complex with Open-Cubane Core: Structure,Spectroscopic and Luminescence Properties

A new open-cubane Mn^III, [{(H₂O)Mn^IIIL}{Mn^IIIL}]₂·2(CH₃OH).2(CH₃CH₂OH)·2Cl, 1 where H ₂ L=[N-(2-hydroxyethyl)-3-methoxysalicylaldimine] has been synthesized and characterized by element analysis, FT-IR, solid UV–Vis spectroscopy and single crystal X-ray diffraction. The crystal structure determination shows an open-cubane tetranuclear complex. The Mn1 (Mn1ⁱ) ions is hexacoordinate by NO₅ donor sets while the Mn2 (Mn2ⁱ) is pentacoordinate by NO₄ donor sets. The solid state photoluminescence properties of complex 1 and its ligand H ₂ L have been investigated under UV light at 349 nm in the visible region. H ₂ L exhibits blue emission while complex 1 shows orange-red emission at room temperature. Variable-temperature magnetic susceptibility measurements on the complex 1 in the range 2–300 K indicate an antiferromagnetic interaction.     

Squaric acid-based peptidic inhibitors of matrix metalloprotease-1

[structure: see text] A series of squaric acid-peptide conjugates were synthesized and evaluated as inhibitors of MMP-1. The cyclobut-3-enedione core was substituted at the 3-position with several functional groups, such as -N(alkyl)OH, -NHOH, and -OH, that are designed to bind to the zinc atom in the active site of the metalloprotease. The 4-position of the cyclobut-3-enedione was derivatized with mono- or dipeptides that are designed to bind in the S1' and S2' subsites of the enzyme, and position the metal chelating group appropriately in the active site for binding to zinc. Positional scanning revealed that -N(Me)OH provided the highest level of inhibition among the chelating groups that were tested, and Leu-Tle-NHMe was the preferred amino acid sequence. A combination of these groups yielded an inhibitor with an IC50 value of 95 microM. For one inhibitor, conversion of one of the carbonyl groups on the cyclobut-3-enedione core to a thiocarbonyl group resulted in a 18-fold increase in potency, and yielded a compound with an IC50 value of 15 microM.     

Product spin-orbit state resolved dynamics of the H+H2O and H+D2O abstraction reactions

The product state-resolved dynamics of the reactions H+H(2)O/D(2)O-->OH/OD((2)Pi(Omega);v',N',f )+H(2)/HD have been explored at center-of-mass collision energies around 1.2, 1.4, and 2.5 eV. The experiments employ pulsed laser photolysis coupled with polarized Doppler-resolved laser induced fluorescence detection of the OH/OD radical products. The populations in the OH spin-orbit states at a collision energy of 1.2 eV have been determined for the H+H(2)O reaction, and for low rotational levels they are shown to deviate from the statistical limit. For the H+D(2)O reaction at the highest collision energy studied the OD((2)Pi(3/2),v'=0,N'=1,A') angular distributions show scattering over a wide range of angles with a preference towards the forward direction. The kinetic energy release distributions obtained at 2.5 eV also indicate that the HD coproducts are born with significantly more internal excitation than at 1.4 eV. The OD((2)Pi(3/2),v'=0,N'=1,A') angular and kinetic energy release distributions are almost identical to those of their spin-orbit excited OD((2)Pi(1/2),v'=0,N'=1,A') counterpart. The data are compared with previous experimental measurements at similar collision energies, and with the results of previously published quasiclassical trajectory and quantum mechanical calculations employing the most recently developed potential energy surface. Product OH/OD spin-orbit effects in the reaction are discussed with reference to simple models.     

Contact handle decompositions

We review Giroux's contact handles and contact handle attachments in dimension three and show that a bypass attachment consists of a pair of contact 1 and 2-handles. As an application we describe explicit contact handle decompositions of infinitely many pairwise non-isotopic overtwisted 3-spheres. We also give an alternative proof of the fact that every compact contact 3-manifold (closed or with convex boundary) admits a contact handle decomposition, which is a result originally due to Giroux.     

Results on Nonlocal Boundary Value Problems

In this article, we provide a variational theory for nonlocal problems where nonlocality arises due to the interaction in a given horizon. With this theory, we prove well-posedness results for the weak formulation of nonlocal boundary value problems with Dirichlet, Neumann, and mixed boundary conditions for a class of kernel functions. The motivating application for nonlocal boundary value problems is the scalar stationary peridynamics equation of motion. The well-posedness results support practical kernel functions used in the peridynamics setting.

We also prove a spectral equivalence estimate which leads to a mesh size independent upper bound for the condition number of an underlying discretized operator. This is a fundamental conditioning result that would guide preconditioner construction for nonlocal problems. The estimate is a consequence of a nonlocal Poincaré-type inequality that reveals a horizon size quantification. We provide an example that establishes the sharpness of the upper bound in the spectral equivalence.     

The influence of the sintering temperature on the structural and the magnetic properties of doped manganites: La0.95Ag0.05MnO3 and La0.75Ag0.25MnO3

La_1−xAg_xMnO₃ samples were synthesized by standard sol-gel method with Ag concentrations of x=0.05 and 0.25. The samples from each concentration were pressed and sintered at 1000, 1200 and 1400 °C for 24 h in air for a systematic study. They were examined structurally by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) and magnetically by Magnetic Properties Measurements System (MPMS). AFM and SEM analyses show that surface morphology changes with Ag concentration and sintering temperature (T_S). It was observed that high temperature sintering leads Ag to leave material as determined from EDS analyses. XRD spectra exhibited that the crystal structure changes with Ag concentration while showing pronounced change with the sintering temperature. From the magnetic measurements, the Curie temperatures (T_C) and the isothermal magnetic entropy changes (−ΔSM) were calculated. It was observed that T_C increases with Ag concentration and decreases with T_S. The maximum −ΔSM was calculated to be 7.2 J/kg K under the field change of 5 T for the sample sintered at 1000 °C with x=0.25.     

Quantum mechanical calculations of tryptophan and comparison with conformations in native proteins

We report a detailed analysis of the potential energy surface of N-acetyl-l-tryptophan-N-methylamide, (NATMA) both in the gas phase and in solution. The minima are identified using the density-functional-theory (DFT) with the 6-31g(d) basis set. The full potential energy surface in terms of torsional angles is spanned starting from various initial configurations. We were able to locate 77 distinct L-minima. The calculated energy maps correspond to the intrinsic conformational propensities of the individual NATMA molecule. We show that these conformations are essentially similar to the conformations of tryptophan in native proteins. For this reason, we compare the results of DFT calculations in the gas and solution phases with native state conformations of tryptophan obtained from a protein library. In native proteins, tryptophan conformations have strong preferences for the beta sheet, right-handed helix, tight turn, and bridge structures. The conformations calculated by DFT, the solution-phase results in particular, for the single tryptophan residue are in agreement with native state values obtained from the Protein Data Bank.