Peptide‐poly(tert‐butyl methacrylate) conjugate into composite micelles in organic solvents versus peptide‐poly(methacrylic acid) conjugate into spherical and worm‐like micelles in water: Synthesis and self‐assembly

Peptide–polymer conjugates are versatile class of biomaterials composed of a peptide block covalently linked with a synthetic polymer block. This report demonstrates the synthesis of peptide‐poly(tert‐butyl methacrylate) (Peptide‐P^tBMA) conjugates of varying molecular weights via a “grafting from” atom transfer radical polymerization (ATRP) technique using as‐synthesized peptide‐based initiator in toluene. Peptide‐P^tBMA conjugate is soluble in many organic solvents and undergoes self‐assembly into micro/nanospheres in DMF/THF as observed from both FESEM and DLS results. The conjugate micro/nanospheres are nothing but the composite micelles formed by the secondary aggregation of primary micelles generated initially in these organic solvents. The hydrolysis of tert‐butyl groups of Peptide‐P^tBMA conjugate leads to the formation of peptide‐poly(methacrylic acid) (Peptide‐PMA) conjugate. The circular dichroism (CD) analysis exhibits the presence of β‐sheet conformation of peptide moiety in synthesized conjugates. The formed Peptide‐PMA conjugate is soluble in water and owing to its amphiphilic character, the conjugate molecules self‐assemble into spherical micelles as well as worm‐like micelles upon increasing the concentration of conjugate in water. However, the sodium salt of Peptide‐PMA conjugates (Peptide‐PMAS) self‐assembles into only spherical swollen micelles in water at higher (pH ～10). The critical aggregation concentrations (CACs) of both Peptide‐PMA and Peptide‐PMAS micelles are measured by fluorescence spectroscopy. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3019–3031     

Importance of unpaired electrons in organic electronics

The first observation that PBBTPD, a low bandgap, ambipolar conjugated donor-acceptor (DA) polymer based on benzobisthiadiazole (BBT), possesses an open-shell singlet ground state as well as a thermally accessible triplet state is described. Similarly, interesting electronic behavior in semiconducting organic DA oligomers based on BBT is also observed. Theoretical predictions have suggested that such behavior is due to the biradicaloid character of BBT and we provide experimental evidence indicating that these predictions are correct. Furthermore, the open shell character strengthens as the conjugation length increases, as observed in the BBT-based polymer, PBBTPD. We show that this biradicaloid structure is observed in each BBT moiety along the chain and that therefore PBBTPD is in fact a polyradicaloid. This observation will most likely aid in the development of better n-type polymeric acceptors for organic semiconductor applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 287–293     

Solid membrane sensor for potassium ions

Titanium ferricyanide gel is found to possess good ion-exchange capacity, mechanical and chemical stability, and selectivity. An Araldite-based membrane of this compound can be used to estimate K⁺ ions in the concentration range 10^–1–10^–4 M. The sensor has a very short response time and remains stable for 2 to 3 months. There is no serious interference by bivalent and multivalent ions. Among the monovalent cations only Na⁺ and NH ₄ ⁺ may cause significant interference.     

Effect of a NAPL on migration of PCP in soil columns

Applied Biochemistry and Biotechnology - Pentachlorophenol (PCP) is a widely used wood-treating chemical that is applied to wood under pressure in the form of concentrated solution in solvents that...     

Reasons for and Consequences of the Mysterious Behaviour of Newly Prepared Hemipyridine Solvate of Bis(pyridine)silver(I) Permanganate,Agpy<Subscript>2</Subscript>MnO<Subscript>4</Subscript>*0.5py

Compositions and chemical identities of compounds formed in silver–permanganate–pyridine–water systems, as well as of their recrystallization products obtained from benzene–acetone solutions, have been elucidated. Three compounds: Agpy₂MnO₄ (1), 7Agpy₂MnO₄*Agpy₄MnO₄ (Agpy_2.25MnO₄) (2) and Agpy₂MnO₄ * 0.5py (Agpy_2.5MnO₄) (3) were isolated. The compositions of the products obtained by a method described previously [1] for the preparation of ‘Agpy₂MnO₄’ (1*) and ‘Agpy_2.5MnO₄’ (2*) were determined and the constituent compounds identified. It has been established that the instability of compound (3) is due to the presence of the benzene, substituting for pyridine at the solvate sites. The benzene, however, is released at room temperature, disrupting the crystal lattice of (3), and the whole process leads to the loss of the solvate pyridine and to the formation of (1).     

Spectrophotometric study of the chelate of palladium(II) with methylthymol blue

Methylthymol blue reacts very sensitively with palladium(II) to form two complexes. The 1:1 complex has λ_max at 530 nm in acidity range 0.02 to 0.05 M with respect to perchloric acid and 1:2 (metal reagent ratio) complex at 500 nm in pH range 6.8 to 7.5. Optimum conditions including the range for adherence to Beer's law, effect of pH, effect of excess reagent and sensitivity are reported for the photometric determination of palladium using methylthymol blue.     

The first report of unusual flipping of the cycloadducts from 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to N-cinnamoyl piperidines

A series of cycloadducts possessing unusual flipping modes have been isolated from the 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to piperidides of cinnamic acid and para-substituted cinnamic acids and these were analyzed by X-ray crystallography to reveal novel solid-state structures. The presence of two different flippomers arising due to flipping of the six/five bicyclic ring was confirmed both in solid state and in solution. This is the first observation of 1,3-dipolar cycloadducts having two different flippomers arising due to flipping of the isoxazolidine ring.