Discovery and Genetic Code Expansion of a Polyethylene Terephthalate (PET) Hydrolase from the Human Saliva Metagenome for the Degradation and Bio-Functionalization of PET.

We report a bioinformatic workflow and subsequent discovery of a new polyethylene terephthalate (PET) hydrolase, which we named MG8, from the human saliva metagenome. MG8 has robust PET plastic degradation activities under different temperature and salinity conditions, outperforming several naturally occurring and engineered hydrolases in degrading PET. Moreover, we genetically encoded 2,3-diaminopropionic acid (DAP) in place of the catalytic serine residue of MG8, thereby converting a PET hydrolase into a covalent binder for bio-functionalization of PET. We show that MG8(DAP), in conjunction with a split green fluorescent protein system, can be used to attach protein cargos to PET as well as other polyester plastics. The discovery of a highly active PET hydrolase from the human metagenome-currently an underexplored resource for industrial enzyme discovery-as well as the repurposing of such an enzyme into a plastic functionalization tool, should facilitate ongoing efforts to degrade and maximize reusability of PET.

Plasma nano-modification of poly(ethylene terephthalate) fabric for pigment adhesion enhancement.

Poly(ethylene terephthalate) (PET) fabrics were modified by treating with radio frequency (RF) plasma of different gases, including argon (Ar), nitrogen (N2), oxygen (O2) and sulfur hexafluoride (SF6), under varied power (50-150 watt) and time period (0.5-20 min). Observations indicated that plasma has affected the morphology and roughness of PET fiber surface in the nano-scale level. After plasma treatment, test patterns were printed by inkjet printer directly onto the sample surface. The enhancement of color printing performance on PET fabric by plasma treatment was evaluated by color spectroscopy. The surface nano-modified PET fabrics by Ar, N2, O2, and SF6 plasmas all exhibited enhanced color yield. AFM, SEM, FTIR-ATR and XPS results suggested that the improved pigment color yield was neither clearly contributed by the wettability of the fabrics nor the polar group induced onto the fiber surfaces but rather mainly by the alteration of surface roughness.

Coating of diamond-like carbon nanofilm on alumina by microwave plasma enhanced chemical vapor deposition process.

Diamond-like carbon (DLC) nanofilms with thickness varied from under one hundred to a few hundred nanometers have been successfully deposited on alumina substrates by microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. To obtain dense continuous DLC nanofilm coating over the entire sample surface, alumina substrates were pre-treated to enhance the nucleation density. Raman spectra of DLC films on samples showed distinct diamond peak at around 1332 cm(-1), and the broad band of amorphous carbon phase at around 1550 cm(-1). Full width at half maximum height (FWHM) values indicated good formation of diamond phase in all films. The result of nano-indentation test show that the hardness of alumina samples increase from 7.3 +/- 2.0 GPa in uncoated samples to 15.8 +/- 4.5-52.2 +/- 2.1 GPa in samples coated with DLC depending on the process conditions. It is observed that the hardness values are still in good range although the thickness of the films is less than a hundred nanometer.

Surface nanomodification of cotton fiber for flame retardant application.

This paper presents efficient surface modification methodology to increase fire resistance properties of cotton by radio frequency (RF) plasma-induced graft copolymerization of vinyl phosphate ester as nanometer residue structure onto cotton surface. Methacryloyloxyethyl diphenyl phosphate (MEDP) monomer was synthesized and grafted onto the surface of cotton fabric by argon RF plasma at ambient temperature. Under optimum RF power (30 W), amounts of MEDP and N,N methylenebisacrylamide cross linking agent were varied to obtain optimum graft copolymerization conditions. Untreated and treated cotton were characterized by attenuated total reflectance infrared (ATR-IR) spectroscopy to investigate their functional group characteristics. This showed a strong covalent attachment between the surface of cotton and flame retardant material as the carbonyl functionality of the MEDP was clearly observed in the spectra. Scanning electron microscopic (SEM) analysis also showed grafted material as nanometer residue on cotton surface. Thermogravimetric analysis (TGA) revealed that the decomposition of phosphorus compound which occurs at lower temperature than the cotton itself resulted in the formation of char which covers cotton surface. This protects the fabric surface from further burning, therefore, higher amounts of remaining materials were observed as char in all cases. Furthermore, limiting oxygen index (LOI) had increased from 19 in untreated to 28 in grafted cotton. Detailed analysis on structural and thermal properties as well as surface grafting efficiency are presented.

Organocatalyzed asymmetric alpha-oxidation, alpha-aminoxylation and alpha-amination of carbonyl compounds.

Organocatalytic asymmetric alpha-oxidation and amination reactions of carbonyl compounds are highly useful synthetic methodologies, especially in generating chiral building blocks that previously have not been easily accessible by traditional methods. The concept is relatively new and therefore the list of new catalysts, oxidizing and aminating reagents, as well as new substrates, are expanding at an amazing rate. The scope of this review includes new reactions and catalysts, mechanistic aspects and synthetic applications of alpha-oxidation, hydroxylation, aminoxylation, amination, hydrazination, hydroxyamination and related alpha-heteroatom functionalization of aldehydes, ketones and related active methylene compounds published during 2005-2009.

Stilbene-bridged tert-butylcalix[4]arene as photoswitchable molecular receptors.

Using a designed control of conformations of tert-butylcalix[4]arene between cone and pinched cone, a highly selective receptor for small electron-deficient molecules with photoswitching binding ability was attained. [reaction: see text]

Effect of amino substituents on the stereochemical outcome of the photo-Arbuzov rearrangements of 1-arylethyl phosphorodiamidites.

The essentially stereochemically pure 1-arylethyl phosphorodiamidites 8 and 9 were irradiated by UV light in acetonitrile, benzene, and cyclohexane (Tables 1-4). Reaction via singlet free-radical pairs, formed by carbon-oxygen bond scission (Scheme 1), which are somewhat longer lived than those from the analogous phosphites 5 and 6, is proposed. Tetramethyl 1-phenylethylphosphorodiamidite (8) gives the photo-Arbuzov rearrangement product 10 in 59% +/- 2% GC yield, based on percent 8 consumed (Tables 1 and 4), along with the free radical dimerization product 2,3-diphenylbutane, 12a, in in amounts corresponding to ca. 19% of the potentially formed 1-phenylethyl radicals. Similarly, from 9, the photorearrangement product 11 is generated in 64 +/- 4% yield (Tables 2 and 4) along with a 18 +/- 2% accountability of the 1-naphthylethyl radicals as 12b. The photorearrangement of stereochemically enriched 8 (R/S = 99:1) gives 10 in which an apparent 67 +/- 2% (100y, eq 3, Table 4) of the initial radical pairs [3,14] recombine with retention of configuration at the stereogenic carbon (34 +/- 3% net retention, eq 5). With TEMPO present, 70% (100y, eq 3) of the initial 1-phenylethyl radicals, 14, from 8 combine with radicals 3 in the solvent cage with retained configuration at carbon (40% percent net retention, eq 5). The yield of product 10 is reduced to 54%, and 12a is absent. Similarly, the five-membered ring naphthylethyl analogue, phosphorodiamidite 9 (R/S = 98:2), affords largely (R)-11 with apparent 34 +/- 3% net retention. The degree of stereorandomization observed in these systems is higher than was reported previously for phosphites 5 and 6. The neglect of reconversion of pro-S 14 to pro-R 14 on the results of these studies is addressed. Estimated maximum values (eq 4) of kcomb/krot (2.3) for the proximate radical pairs [3,14] from 8 with TEMPO present appear to be at least 6-fold smaller than those of the analogous phosphite (R)-5 (average kcomb/krot = 13 with TEMPO present). Possible origins for this effect are proposed.