Epimerization‐Free Block Synthesis of Peptides from Thioacids and Amines with the Sanger and Mukaiyama Reagents

Highly activated thioesters formed by the rapid reaction of C‐terminal thioacids derived from protected amino acids and peptides with the Sanger reagent and other electron‐deficient aryl halides in the presence of a free amine immediately form a peptide bond with the amine. This essentially epimerization‐free method was used for the 4+4 block synthesis of a hindered octapeptide (see scheme; Boc, Pbf, and Trt are protecting groups).

     

Effects of Monomer Functionality on Switchable Holographic Gratings Formed in Polymer‐Dispersed Liquid‐Crystal Cells

Switching characteristics: The 633 nm wavelength of an He–Ne laser is used to fabricate holographic transmission gratings in polymer‐dispersed liquid‐crystal cells. The microstructure and diffraction efficiency (η) both improve with increasing functionality (see figure). For functionalities of 2.5 or more, η approaches 34 % and can be switched off with electric fields of about 20 MV m^?1.

     

Zwitterionic molecularly imprinted polymer‐based solid‐phase micro‐extraction coupled with molecularly imprinted polymer sensor for ultra‐trace sensing of L‐histidine

The proposed L ‐histidine sensing system composed of a molecularly imprinted solid‐phase microextraction component combined with a molecularly imprinted polymer sensor was used to determine critical levels of test analyte in a complex matrix of highly diluted human blood serum without any non‐specific sorption and false‐positive contributions. The molecularly imprinted polymer was a zwitterionic polymer brush derived from the disodium salt of EDTA and chloranil, grafted to solid‐phase microextraction material. The hyphenated approach was able to detect L ‐histidine quantitatively with a limit of detection as low as 0.0435 ng/mL (RSD = 0.2%, S/N = 3).     

Single-molecule spectroscopy of fluorescent proteins

The discovery and use of fluorescent proteins has revolutionized cellular biology. Despite the widespread use of visible fluorescent proteins as reporters and sensors in cellular environments the versatile photophysics of fluorescent proteins is still subject to intense research. Understanding the details of the photophysics of these reporters is essential for accurate interpretation of the biological and biochemical processes illuminated by fluorescent proteins. Some aspects of the complex photophysics of fluorescent proteins can only be observed and understood at the single-molecule level, which removes averaging inherent to ensemble studies. In this paper we review how single-molecule emission detection has helped understanding of the complex photophysics of fluorescent proteins.

Electrochemical behavior of different structural states of the alloy Ti60Ni40

Potentiodynamic polarization studies were carried out on nanocrystalline I, nanocrystalline II and nanocrystalline III states having crystallite size 35 ± 5 nm, 18 ± 2 nm and 10 ± 2 nm of the alloy Ti₆₀Ni₄₀ in 1 M H₂SO₄ aqueous medium. It was observed that the nanocrystalline III state exhibits superior corrosion resistance as compared to the nanocrystalline II and nanocrystalline I states of the alloy Ti₆₀Ni₄₀. XPS studies were also performed after corrosion test and it was observed that nanocrystalline III state contains only Ti²⁺ and Ti⁴⁺ species whereas nanocrystalline I and nanocrystalline II state contains Ti²⁺, Ti³⁺and Ti⁴⁺ along with some unoxidized metallic Ti⁰ in the case of nanocrystalline I state. Thus the small crystallite size and the presence of only Ti²⁺ and Ti⁴⁺ species in the form of TiO and TiO₂ leads to the formation of a protective oxide film which is adherent, stable and improves the corrosion resistance of the nanocrystalline III state of the alloy Ti₆₀Ni₄₀.     

Crystal Structure Studies of Two Regioisomers of Bromo-4-Aryloxymethylcoumarins

Abstract  

The 4-(2-bromo-4-methyl-phenoxymethyl)-6-methylcoumarin (1) have been synthesized from bromination of corresponding 4-aryloxymethyl coumarin, which is a regioisomer of 4-(2-bromo-4-methyl-phenoxymethyl)-7-methylcoumarin (2) (CCDC-695895). The compound 1 crystallizes with triclinic space group P-1, a = 8.0943(3) ?, b = 9.3502(3) ?, c = 10.1476(4) ?, α = 90.234(2)°, β = 94.065(2)°, γ = 95.106(2)°, Z = 2 and compound 2 crystallizes with monoclinic space group P2₁/n, a = 8.465(5) ?, b = 13.649(5) ?, c = 13.304(5) ?, α = 90.000(5)°, β = 90.740(5)°, γ = 90.000(5)°, Z = 4. Both the compounds are planar with variation in their intermolecular hydrogen bonds between C–H···O and C–H···π.     

Isolation and Crystal Structure of 6α,7α-Epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide monohydrate-A Withasteroid from Withania somnifera Leaves

Abstract  

(5R,6S,7S,8S,9S,10R,13S,14S,17S,20R,22R)-6α,7α-epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide has been isolated from Withania somnifera leaves. Three-dimensional X-ray intensity data were collected at 293 K on Bruker CCD area-detector diffractometer equipped with graphite-monochromated MoKα radiation (λ = 0.71073 ?). The compound crystallizes in monoclinic space group P21 with unit cell parameters: a = 6.4540(2), b = 11.3656(4), c = 17.4982(5) ?, β = 90.730 ^o(2), Z = 2. The crystal structure was refined to a final R-value of 0.0419 for 6122 observed reflections. One water solvent molecule was observed. All the rings of the steroid skeleton are trans connected. Rings A and B exists in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between half-chair and envelope. The δ-lactone ring E adopts a distorted sofa conformation. The characteristic pattern observed in the packing diagram is the appearance of twisted chains of molecules. The packing of the molecules in the crystal is stabilized by intra- and intermolecular O–H···O and C–H···O interactions.     

Revisiting the shelf life constrained multi-product manufacturing problem

A multi-product manufacturing problem generally consists of the total cost minimization. In case where the shelf life constraint is imposed, various options to deal with the situation are widely discussed in the literature. These options include a reduction in the production rate and cycle time separately, and the simultaneous reduction of production rate and cycle time. When the production rate is decreased, the unit manufacturing cost increases and because of this the inventory holding costs need modification. In the existing literature, this has been ignored in the computation of cost and therefore a revisit to the problem has been justified. The present paper modifies the holding cost and this problem has been reformulated for the basic case. This has also been extended for an inclusion of shortages that are backordered completely or partially.     

Higher-Order Duality in Nondifferentiable Minimax Programming with Generalized Type I Functions

A unified higher-order dual for a nondifferentiable minimax programming problem is formulated. Weak, strong and strict converse duality theorems are discussed involving generalized higher-order (F,α,ρ,d)-Type I functions. The research of second author was supported by the Department of Atomic Energy, Government of India, under the NBHM Post Doctoral Fellowship Program 40/9/2005-R&D II/2398.