Fluorogenic Ag+–Tetrazolate Aggregation Enables Efficient Fluorescent Biological Silver Staining

Silver staining, which exploits the special bioaffinity and the chromogenic reduction of silver ions, is an indispensable visualization method in biology. It is a most popular method for in‐gel protein detection. However, it is limited by run‐to‐run variability, background staining, inability for protein quantification, and limited compatibility with mass spectroscopic (MS) analysis; limitations that are largely attributed to the tricky chromogenic visualization. Herein, we reported a novel water‐soluble fluorogenic Ag⁺ probe, the sensing mechanism of which is based on an aggregation‐induced emission (AIE) process driven by tetrazolate‐Ag⁺ interactions. The fluorogenic sensing can substitute the chromogenic reaction, leading to a new fluorescence silver staining method. This new staining method offers sensitive detection of total proteins in polyacrylamide gels with a broad linear dynamic range and robust operations that rival the silver nitrate stain and the best fluorescent stains.     

Gas chromatography/ion trap mass spectrometry applied for the determination of polybrominated diphenyl ethers in soil

A gas chromatography/ion trap mass spectrometry (GC/ITMS) method was developed for the determination of polybrominated diphenyl ethers (PBDEs). ITMS parameters were optimized in order to achieve the best sensitivity for the PBDE analysis. Tandem mass spectrometry, along with an isotope dilution internal standard method, was used for the quantitation. Chromatographic windows were developed for mono- to hepta-BDEs, depending on the retention times when a 30-m GC column was used. A different 15-m column was used to analyze deca-BDE. Environmental soil samples collected from an electronic waste recycling site were prepared by using Soxhlet extraction and column chromatographic cleanup. Average recoveries of 61-118% were obtained for the 13C-labeled PBDE internal standards spiked in the samples prior to sample preparation. The accuracy represented by relative analytical errors was -24% to 18%, and the precision (relative standard deviation) was 11-26% (n=8). The method detection limits ranged from 0.013-0.25 ng/g for the PBDEs in soil.     

Contact angle measurements with liquids consisting of bulky molecules

Well-measured contact angles with different solid-liquid systems fall approximately on smooth patterns when plotted versus liquid surface tension. However, there are deviations of 1 degrees -3 degrees , which are outside the error limits. It is the purpose of this paper to elucidate the reasons for such deviations. Two types of liquids were selected for advancing contact angle measurements on Teflon AF 1600 coated surfaces: a series of n-alkanes ranging from n-hexane to n-hexadecane and five liquids consisting of bulky molecules, octamethylcyclotetrasiloxane (OMCTS), methyl salicylate, tetralin, cis-decalin, and octamethyltrisiloxane (OMTS). It was found that contact angles of the liquids with bulky molecules fall on a perfectly smooth curve corresponding to a solid surface tension of 13.64 +/- 0.1 mJ/m2. However, contact angles of n-alkanes deviated from this curve by up to 3 degrees in a complicated fashion. The observed trend suggests that more than one mechanism is responsible for the deviations. Substrate-induced rearrangement of liquid molecules in the close vicinity of the surface in the case of long-chain n-alkanes and adsorption of vapor onto the solid surface in the case of short-chain n-alkanes are the most likely explanations. The results suggest that liquids with bulky molecules appear to be suitable for contact angle measurements to characterize energetics of polymeric surfaces.     

Structural trends in first-row transition-metal bis(benzimidazole) complexes

Dimethyl-substituted bis(benzimidazole) (Me2BBZ) is a novel macrocyclic ligand that possesses an intrinsic nonplanarity. To examine how metal-ion binding affects the magnitude of this nonplanarity, we have determined the structures of a periodic series of Me2BBZ complexes bound to Mn(II), Fe(II), Co(II), Ni(II), and Cu(II). These studies demonstrate that the extent of ligand ruffling and metal doming is indeed influenced by the nature of the metal. Concomitant with the periodic decrease of the ionic radii of the encapsulated divalent metal ion, a decrease in the magnitude of both the ligand nonplanarity and the metal out-of-the-plane distance is observed. For the metal out-of-the-plane distance, this correlation persists until the metal finally moves into the mean ligand plane. For the nonplanar distortion, the extent of the nonplanarity decreases to a limiting value that is intrinsic to the Me2BBZ ligand due to steric factors. These observations indicate that the relative sizes of the metal ion and the Me2BBZ ligand cavity have profound effects on the structural features of the metal-ligand complex.     

Liquid alkoxides of a perfluorotertiary alcohol and their derivatives

Sodium and lithium alkoxides of (CF₃)₂CFOCF₂CF₂C(CF₃)₂OH have been prepared in high yields by the addition of sodium hydride to the alcohol or in the case of the lithium salt through the addition of (CF₃)₂C=O to the organolithium compound (CF₃)₃CFOCF₂CF₂Li. These salts react with active halides e.g. PCl₃ or cyanuric chloride to yield completely substituted products.     

Water-catalyzed dehalogenation reactions of the isomer of CBr4 and its reaction products and a comparison to analogous reaction of the isomers of di-and trihalomethanes

A combined experimental and theoretical study of the UV photolysis of a typical tetrahalomethane, CBr4, in water and acetonitrile/water was performed. Ultraviolet photolysis of low concentrations of CBr4 in water mostly leads to the production of four HBr leaving groups and CO2. Picosecond time-resolved resonance Raman (Ps-TR3) experiments and ab initio calculations indicate that water-catalyzed O-H insertion/HBr elimination of the isomer of CBr4 and subsequent reactions of its products lead to the formation of these products. The UV photolyses of di-, tri-, and tetrahalomethanes at low concentrations in water-solvated environments are compared to one another. This comparison enables a general reaction scheme to be deduced that can account for the different products produced by UV photolysis of low concentrations of di-, tri-, and tetrahalomethanes in water. The fate of the (halo)formaldehyde intermediate in the chemical reaction mechanism is the key to determining how many strong acid leaving groups are produced and which carbon atom final product is likely formed by UV photolysis of a polyhalomethane at low concentrations in a water-solvated environment.