1. Highly Enantioselective Graphene-Based Chemical Sensors Prepared by Chiral Noncovalent Functionalization
Xiaobo Shang, Cheol Hee Park, Gwan Yeong Jung, Sang Kyu Kwak, Joon Hak Oh ACS Appl Mater Interfaces. 2018 Oct 24;10(42):36194-36201. doi: 10.1021/acsami.8b13517. Epub 2018 Oct 12.
As a basic characteristic of the natural environment and living matter, chirality has been used in various scientific and technological fields. Chiral discrimination is of particular interest owing to its importance in catalysis, organic synthesis, biomedicine, and pharmaceutics. However, it is still very challenging to effectively and selectively sense and separate different enantiomers. Here, enantio-differentiating chemosensor systems have been developed through spontaneous chiral functionalization of the surface of graphene field-effect transistors (GFETs). GFET sensors functionalized using noncovalent interactions between graphene and a newly synthesized chiral-functionalized pyrene material, Boc-l-Phe-Pyrene, exhibit highly enantioselective detection of natural acryclic monoterpenoid enantiomers, that is, ( R)-(+)- and ( S)-(-)-β-citronellol. On the basis of a computational study, the origin of enantio-differentiation is assigned to the discriminable charge transfer from ( R)-(+)- or ( S)-(-)-β-citronellol into graphene with a significant difference in binding strength depending on surface morphology. The chemosensor system developed herein has great potential to be applied in miniaturized and rapid enantioselective sensing with high sensitivity and selectivity.
2. Synthetic and pharmacological studies on longicalycinin A
Rajiv Dahiya Pak J Pharm Sci. 2007 Oct;20(4):317-23.
Present investigation describes the synthesis of a natural phenylalanine-rich cyclopolypeptide longicalycinin A (10) by coupling of dipeptide unit Boc-L-phe-L-tyr-OH with tripeptide unit L-pro-L-phe-gly-OMe followed by cyclization of linear segment. Synthesized cyclic pentapeptide was characterized by spectral techniques including FTIR, 1H/13C NMR, FAB MS and elemental analysis and screened for different pharmacological activities. It was found that it has good anthelmintic activity against Megascoplex konkanensis, Pontoscotex corethruses and Eudrilus sp. at 2 mg/ml concentration, in addition to high cytotoxicity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines with CTC50 values of 2.62 and 6.37 microM. Dermatophytes were found to be moderately sensitive towards newly synthesized peptide.
3. Synthesis, crystal structure, and molecular conformation of N-Boc-L-Phe-dehydro-Leu-L-Val-OCH3
P Narula, H C Patel, T P Singh, V S Chauhan Biopolymers. 1990 May-Jun;29(6-7):935-41. doi: 10.1002/bip.360290606.
The peptide N-Boc-L-Phe-dehydro-Leu-L-Val-OCH3 was synthesized by the usual workup procedure and finally by coupling the N-Boc-L-Phe-dehydro-Leu-OH to valine methyl ester. It was crystallized from its solution in methanol-water mixture at 4 degrees C. The crystals belong to the triclinic space group P1 with a = 5.972(5) A, b = 9.455(6) A, c = 13.101(6) A, alpha = 103.00(4) degrees, beta = 97.14(5) degrees, gamma = 102.86(5) degrees, V = 690.8(8) A, Z = 1, dm = 1.179(5) Mg m-3 and dc = 1.177(5) Mg m-3. The structure was determined by direct methods using SHELXS86. It was refined by block-diagonal least-squares procedure to an R value of 0.060 for 1674 observed reflections. The C alpha 2-C beta 2 distance of 1.323(9) A in dehydro-Leu is an appropriate double bond length. The bond angle C alpha-C beta-C gamma in the dehydro-Leu residue is 129.4(8) degrees. The peptide backbone torsion angles are theta 1 = -168.6(6) degrees, omega 0 = 170.0(6) degrees, phi 1 = -44.5(9) degrees, psi 1 = 134.5(6) degrees, omega 1 = 177.3(6) degrees, phi 2 = 54.5(9) degrees, psi 2 = 31.1(10) degrees, omega 2 = 171.7(6) degrees, phi 3 = 51.9(8) degrees, psi T3 = 139.0(6) degrees, theta T = -175.7(6) degrees. These values show that the backbone adopts a beta-turn II conformation. As a result of beta-turn, an intramolecular hydrogen bond is formed between the oxygen of the ith residue and NH of the (i + 3)th residue at a distance of 3.134(6) A.(ABSTRACT TRUNCATED AT 250 WORDS)
