Thiol‐Directed Synthesis of Highly Fluorescent Gold Clusters and Their Conversion into Stable Imaging Nanoprobes

Fluorescent gold clusters (FGCs) with tunable emission from blue to red and quantum yields in the range of 6–17 % have been synthesized by simple modification of the conditions used for the synthesis of gold nanoparticles, namely by replacing the stronger reducing agent with a controlled amount of thiol. Various functional FGCs with hydrodynamic diameters of 5–12 nm have been successfully synthesized and used as cell labels. The results of our investigations strongly indicate that FGCs composed of Au⁰ are more stable imaging probes than commonly reported red/NIR‐emitting FGCs with a composition of Au⁰/Au^I, as this combination rapidly transforms into nonfluorescent large clusters on exposure to light. The FGC‐based nanoprobes reported herein exhibit stable fluorescence upon continuous light exposure and can be used as imaging probes with low cytotoxicity.     

Triton-B-Catalyzed,Efficient, One-Pot Synthesis of Carbazates Through Alcoholic Tosylates

A quick, efficient, one-pot synthesis of carbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tert alcohols, with a variety of substituted hydrazines using the benzyltrimethylammonium hydroxide (Triton-B)/CO₂ system. The reaction conditions are mild with simpler workup procedures than the reported methods.     

Efficient Synthesis of Bis(heterocyclyl)methanes

The reaction of pyrrole/furan aldehyde with Grignard reagent and pyrrole/N-methyl pyrrole in sequence allows efficient synthesis of a number of meso-elaborated bis(heterocyclyl)methanes, which are otherwise difficult to obtain through a direct aldehyde condensation route.      

Ultrafiltration of Thin Stillage from Conventional and E-Mill Dry Grind Processes

We used ultrafiltration (UF) to evaluate membrane filtration characteristics of thin stillage and determine solids and nutrient compositions of filtered streams. To obtain thin stillage, corn was fermented using laboratory methods. UF experiments were conducted in batch mode under constant temperature and flow rate conditions. Two regenerated cellulose membranes (10 and 100 kDa molecular weight cutoffs) were evaluated with the objective of retaining solids as well as maximizing permeate flux. Optimum pressures for 10 and 100 kDa membranes were 207 and 69 kPa, respectively. Total solids, ash, and neutral detergent fiber contents of input TS streams of dry grind and E-Mill processes were similar; however, fat and protein contents were different (p < 0.05). Retentate obtained from conventional thin stillage fractionation had higher mean total solids contents (27.6% to 27.8%) compared to E-Mill (22.2% to 23.4%). Total solids in retentate streams were found similar to those from commercial evaporators used in industry (25% to 35% total solids). Fat contents of retentate streams ranged from 16.3% to 17.5% for the conventional process. A 2% increment in fat concentration was observed in the E-Mill retentate stream. Thin stillage ash content was reduced 60% in retentate streams.     

Simultaneous Recovery of Lipids and Proteins by Enzymatic Hydrolysis of Fish Industry Waste Using Different Commercial Proteases

Four different commercial proteases (Protease-P-Amano6, Alcalase^®, Protex 7L^®, and Neutrase^®) were evaluated for recovering lipids and protein simultaneously by hydrolysis. Fungal protease (Protease-P-Amano6) resulted in maximum lipid recovery (74.9%) followed by alcalase (61.7%). Peroxide value (PV; milli-equivalents of oxygen per kilogram) in the oil recovered after hydrolysis was 40.48 compared to 8.7 in lipids from fresh fish viscera. However, addition of tertiary butyl hydroxyl quinine at 200 ppm level maintained the PV of oil recovered by hydrolysis closer to oil from fresh waste. Degree of hydrolysis was the highest in case of fungal protease (49.1%) where neutrase resulted in higher total antioxidant activity (micrograms of ascorbic acid equivalents per milligram protein) of 34.4. Protein hydrolysate prepared using fungal protease had the higher diphenylpicrylhydrazyl radical scavenging activity as compared to those from other enzymes. The results indicate the utility of commercial proteases in providing an ecofriendly and feasible solution for reducing disposal problems associated with fish processing.     

Multiple pathways for benzyl alcohol oxidation by Ru(V)═O3+ and Ru(IV)═O2+

Significant rate enhancements are found for benzyl alcohol oxidation by the Ru(V)═O(3+) form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH(2))](2+) [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru(IV)═O(2+) and for the Ru(IV)═O(2+) form with added bases due to a new pathway, concerted hydride proton transfer (HPT).     

Synthesis and photophysics of an octathioglycosylated zinc(II) phthalocyanine

A water soluble zinc(II) phthalocyanine symmetrically appended with eight thioglucose units was synthesized from commercially available hexadecafluorophthalocyaninatozinc(II) by controlled nucleophilic substitution of the peripheral fluoro groups. The photophysical properties and cancer cell uptake studies of this nonhydrolysable thioglycosylated phthalocyanine are reported. The new compound has amphiphilic character, is chemically stable, and can potentially be used as a photosensitizer in photodynamic therapy.     

Dynamic templating of colloidal patterns in three dimensions with nonuniform electric fields

Order-disorder transitions in colloidal systems are an attractive option for making switchable materials. Electric-field-driven order-disorder transitions are especially attractive for this purpose because the tuning parameter is easily and externally controllable. However, precise positional control of 3D structure is immensely challenging. Using patterned electrodes, we demonstrate that ac electric fields-dominantly dielectrophoresis (DEP) coupled with an electrohydrodynamic mechanism consisting of induced-charge electro-osmosis (ICEO)-can be used to template colloidal order dynamically in three dimensions. We find that the electric field geometry dictates the location, size, and shape of colloidal patterns and can produce patterns with surprising complexity.     

Comparative molecular chemistry of molybdenum and tungsten and its relation to hydroxylase and oxotransferase enzymes

The similarities and differences in the fundamental coordination chemistry of molybdenum and tungsten mainly in physiological oxidation states M^IV–VI are examined in relation to the properties of enzyme sites that catalyze oxygen atom transfer reactions. The comparative aspects of dithiolene complexes, which as synthetic analogues simulate structural and electronic features of these sites, are emphasized. Analogue reaction systems of enzymes are summarized. The mechanism of reduction of the biological substrate Me₂SO in one such system as elucidated with density functional calculations is presented as a case study.