Amphiphilic Peptide–Polymer Conjugates with Side‐Conjugation

Polymers conjugated to the exterior of a protein mediate its interactions with surroundings, enhance its processability and can be used to direct its macroscopic assemblies. Most studies to date have focused on peptide–polymer conjugates based on hydrophilic polymers. Engineering amphiphilicity into protein motifs by covalently linking hydrophobic polymers has the potential to interface peptides and proteins with synthetic polymers, organic solvents, and lipids to fabricate functional hybrid materials. Here, we synthesized amphiphilic peptide–polymer conjugates in which a hydrophobic polymer is conjugated to the exterior of a heme‐binding four‐helix bundle and systematically investigated the effects of the hydrophobicity of the conjugated polymer on the peptide structure and the integrity of the heme‐binding pocket. In aqueous solution with surfactants present, the side‐conjugated hydrophobic polymers unfold peptides and may induce an α‐helix to β‐sheet conformational transition. These effects decrease as the polymer becomes less hydrophobic and directly correlate with the polymer hydrophobicity. Upon adding organic solvent to solubilize the hydrophobic polymers, however, the deleterious effects of hydrophobic polymers on the peptide structures can be eliminated. Present studies demonstrate that protein structure is sensitive to the local environment. It is feasible to dissolve amphiphilic peptide–polymer conjugates in organic solvents to enhance their solution processability while maintaining the protein structures.

     

Aspect ratio dependence on surface enhanced Raman scattering using silver and gold nanorod substrates

Silver and gold nanorods with aspect ratios from 1 to 16 have been used as substrates for surface enhanced Raman spectroscopy (SERS) in colloidal solution. The nanorod aspect ratio is varied to give different degrees of overlap between the nanorod longitudinal plasmon band and excitation source in order to determine its effect on overall surface enhancement. Results suggest that enhancement factors are a factor of 10-10(2) greater for substrates that have plasmon band overlap with the excitation source than for substrates whose plasmon bands do not.     

Photoinduced intramolecular charge transfer reaction in (E)-3-(4-Methylamino-phenyl)-acrylic acid methyl ester: A fluorescence study in combination with TDDFT calculation

A donor-acceptor substituted aromatic system (E)-3-(4-Methylamino-phenyl)-acrylic acid methyl ester (MAPAME) has been synthesized, and its photophysical behavior obtained spectroscopically has been compared with the theoretical results. The observed dual fluorescence from MAPAME has been assigned to emission from locally excited and twisted intramolecular charge transfer states. The donor and acceptor angular dependency on the ground and excited states potential energy surfaces have been calculated both in vacuo and in acetonitrile solvent using time dependent density functional theory (TDDFT) and TDDFT polarized continuum model (TDDFT-PCM), respectively. Calculation predicts that a stabilized twisted excited state is responsible for red shifted charge transfer emission.     

Design of medium energy beam transport line between the RFQ and the Linac in the radioactive ion beam facility at VECC,Kolkata

The design of a medium energy beam transport (MEBT) line comprising of a re-buncher and four quadrupoles, two upstream and the other two downstream of the re-buncher, has been presented. The design was done to ensure almost 100% transport of heavy-ion beams of about 99 keV/u energy from RFQ having a q/A not less than 1/14 through the re-buncher and then through IH Linac of about 0.6 m length in which beam would be accelerated to about 185 keV/u. The re-buncher has been designed to operate at 37.8 MHz, the resonating frequency of both the RFQ and the IH Linac. The entire beam line has been installed and recently O⁵⁺ beam from RFQ has been transported through the re-buncher and subsequently accelerated in the IH Linac successfully.     

Effect of progressive annealing on Silicon Nanostructures grown by Hot Wire Chemical Vapor Deposition

In this work, the evolution of Silicon Nanostructures with progressive annealing has been studied. Hot Wire CVD (HWCVD) process was used to deposit a Si_xN_y/a-Si structure on an n-type 〈100〉$〈100〉$ Silicon substrate with the Nitride acting as the buffer layer. The depositions were carried out at a low substrate temperature (250 °C) which is precisely why HWCVD was chosen over other processes for this work. The as-deposited sample was then annealed at 800 °C and 900 °C respectively. AFM studies revealed promising results hinting at the presence of Silicon Nanostructures. With progressive annealing the Nanostructures began to evolve, eventually turning into sharp Nanopillars upon annealing at 900 °C. In this paper, a growth model has been proposed which attempts to validate the experimental results. Though a lot of work is currently underway in this field, study of Silicon Nanostructures grown by HWCVD technique is relatively new.     

Minimal logarithmic signatures for finite groups of Lie type

A logarithmic signature (LS) for a finite group G is an ordered tuple α =  [A ₁, A ₂, . . . , A _n ] of subsets A _i of G, such that every element ${g \in G}$ can be expressed uniquely as a product g =  a ₁ a ₂ . . . a _n , where ${a_i \in A_i}$ . The length of an LS α is defined to be ${l(\alpha)= \sum^{n}_{i=1}|A_i|}$ . It can be easily seen that for a group G of order ${\prod^k_{j=1}{p_j}^{m_j}}$ , the length of any LS α for G, satisfies, ${l(\alpha) \geq \sum^k_{j=1}m_jp_j}$ . An LS for which this lower bound is achieved is called a minimal logarithmic signature (MLS) (González Vasco et al., Tatra Mt. Math. Publ. 25:2337, 2002). The MLS conjecture states that every finite simple group has an MLS. This paper addresses the MLS conjecture for classical groups of Lie type and is shown to be true for the families PSL _n (q) and PSp _2n (q). Our methods use Singer subgroups and the Levi decomposition of parabolic subgroups for these groups.