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[FeFe] hydrogenases demonstrate remarkable catalytic efficiency in hydrogen evolution and oxidation processes. However, susceptibility of these enzymes to oxygen‐induced degradation impedes their practical deployment in hydrogen‐production devices and fuel cells. Recent investigations into the oxygen‐stable (Hinact) state of the H‐cluster revealed its inherent capacity to resist oxygen degradation. Herein, we present findings on Cl‐ and SH‐bound [2Fe‐2S] complexes, bearing relevance to the oxygen‐stable state within a biological context. A characteristic attribute of these complexes is the terminal Cl−/SH− ligation to the iron center bearing the CO bridge. Structural analysis of the t‐Cl demonstrates a striking resemblance to the Hinact state of DdHydAB and CbA5H. The t‐Cl/t‐SH exhibit reversible oxidation, with both redox species, electronically, being the first biomimetic analogs to the Htrans and Hinact states. These complexes exhibit notable resistance against oxygen‐induced decomposition, supporting the potential oxygen‐resistant nature of the Htrans and Hinact states. The swift reductive release of the Cl‐/SH‐group demonstrates its labile and kinetically controlled binding. The findings garnered from these investigations offer valuable insights into properties of the enzymatic O2‐stable state, and key factors governing deactivation and reactivation conversion. This work contributes to the advancement of bio‐inspired molecular catalysts and the integration of enzymes and artificial catalysts into H2‐evolution devices and fuel‐cell applications. [ABSTRACT FROM AUTHOR]

Fe3(CO)12 reacted with azadiethylthiols afforded [Fe2(μ‐S(CH2)2NR(CH2)2S)(CO)6]2 (R = nPr, 1A; iPr, 2A). Structure analysis revealed that 1A features the anti‐(a,e,a,e) configuration, while its iso‐propyl 2A adopts the syn‐(a,e,a,e) arrangement. NMR measurements at room temperature confirmed this structure, showing distinct signals for 2 NCH2 and 2 SCH2 methylene groups. Acid treatment of 1–2 yielded N‐protonated species (1A–H, 2A–H), maintaining the anti‐(a,e,a,e) configuration. Isolation of 1B–H revealed both the syn‐(a,e,e,a) and anti‐(a,e,e,a) configuration by X‐ray single‐crystallography. Protonation of 1A–H induced downfield shifts in methylene proton signals, with NH hydrogen recorded at 6.96 ppm. Furthermore, 1B–H displays similar NMR behavior, indicating the coexistence of two isomeric molecules of 1B–H, syn‐(a,e,e,a) and anti‐(a,e,e,a), which is consistent with the crystallographic results. Moreover, ion mobility‐mass spectrometry (IM‐MS) is harnessed for the swift identification and differentiation of these isomeric complexes in solution. By leveraging accurate mass measurements and MS/MS analyses, the molecular formula and constituents are validated. The sample mobility enables straightforward characterization of 1A, 1B, and 2A in relation to their stereo‐ and regio‐configurations, obviating the need for extensive time or sample quantities. Integration of findings from X‐ray crystallography, NMR, and IM‐MS furnishes precise and comprehensive structural insights into the coordination complexes. [ABSTRACT FROM AUTHOR]

The existence of surfactants in proteomics samples can severely reduce enzymatic digestion efficiency, liquid chromatography (LC) separation efficiency, column lifetime, and mass spectrometry (MS) sensitivity. Although various techniques are able to remove surfactants, surfartants may occasionally be retained in samples due to variations in sample preparation method or personal skill. Evaluation of surfactant residue in a sample, however, usually requires an additional instrument and is time-consuming. In this study, a simple and rapid visual indicator for surfactant abundance (VISA) was developed. With the detection of a visible surfactant pellet in the solution, this assay was able to detect surfactant residue in aqueous solutions within 5 min. Without the need of additional equipment such as a mass spectrometer, every user can perform a quick test on their bench before sending the sample to the MS facility. The detection limit for the commonly used surfactants, Triton X-114 and SDS, was about 0.0005% and 0.0002%, respectively. The VISA was successfully applied to evaluate the efficiency of removal of surfactants in Triton X-114 extracted membrane proteins using tube-gel. With the combination of Triton X-114 extraction and tube-gel protocol, a study of spermatozoa membrane proteome identified about 252 proteins of which about 67.5% were classified as membrane proteins. The coexistence of protein and surfactant did not affect the VISA sensitivity, suggesting that this indicator is suitable for proteomics applications. The VISA also has potential for the detection of other surfactants and can be applied to other surfactant removing protocols. 10.1021/ac1017937

A robust interface has been developed for interfacing micellar electrokinetic chromatography (MEKC) and nonvolatile buffer capillary electrophoresis (CE) to electrospray ionization mass spectrometry (ESI-MS). The interface consists of two parallel capillaries for separation (50 [micro]m i.d. x 155 [micro]m o.d.) and makeup (50 [micro]m i.d. x 155 [micro]m o.d.) housed within a larger capillary (530 [micro]m i.d. x 690 [micro]m o.d.). The capillaries terminate in a single tapered tip having a beveled edge. The use of a tapered beveled edge results in a greater tip orifice diameter (75 [micro]m) than in a previous design from our laboratory (25 [micro]m) that used a flat tip. While maintaining a similar optimum flow rate and consequently similar sample dilution, a 75-[micro]m beveled emitter is more rugged than a 25-[micro]m flat tip. Furthermore, the incorporation of a sheath liquid capillary allows the compositions of the final spray solution to be controlled. The application of this novel CE/ESI-MS interface was demonstrated for MEKC using mixtures of triazines (positive ion mode) and phenols (negative ion mode). The ability to perform CE/ESI-MS using a nonvolatile buffer was demonstrated by the analysis of gangliosides with a buffer consisting of 40 mM borate and 20 mM [alpha]-cyclodextrin.

A simple and versatile low-flow interface has been developed for interfacing capillary electrophoresis (CE) with electrospray ionization (ESI) mass spectrometry. This low-flow interface showed better sensitivity than a conventional sheath liquid interface, primarily attributed to a low dilution factor and a reduction in the sprayer orifice size. The interface was also found to be more tolerant to the presence of nonvolatile salts. Because of tolerance to the surfactant SDS, this interface can be used to couple micellar electrokinetic chromatography (MEKC) with ESI-MS. The performance of the interface in an MEKC-MS application, as demonstrated in the analysis of triazines, was significantly better than that obtained with a conventional sheath liquid interface. Moreover, this interface can be easily used for large-volume sample-stacking (LVSS) applications. Using a series of phenols as a test case, an approximate 500-fold enrichment was achieved by LVSS in conjunction with the low-flow CE/MS interface described.

Phospholipids are the major components of cellular membranes and possess important biological roles. Despite their significance in diagnosis and therapeutic application in various diseases, systematic profiling of phospholipids remains challenging due to time‐consuming sample preparation and their inherent structure complexity. Taking advantages of complementary, simple, and fast structural analysis by matrix‐assisted laser desorption ionization‐time of flight mass spectrometry (MALDI‐TOF MS) and Fourier transform infrared spectroscopy (FTIR), we reported a nanoprobe‐based dual detection strategy for large‐scale phospholipid profiling. Based on electrostatic interaction between nitrilotriacetic acid (NTA) chelated iron ion and phosphate head on phospholipids, we developed an NTA‐decorated magnetic nanoparticle (MNP)‐based strategy for enrichment of phospholipids from lung cancer cell lines. Compared to the conventional liquid–liquid extraction, NTA@MNP nanoprobe enrichment demonstrated 2.6‐fold more identified phospholipids. By direct on‐particle analysis, FTIR confirmed the P‐O‐C and phosphate stretching characteristic of the phospholipid head group, and MALDI‐TOF MS identified a total of 59 phospholipids from PC9 and A549 lung cancer cells. Comparing the variation of phospholipids between two cell lines, we identified significantly more phospholipids in the PC9 cells (49) compared to 35 phospholipids in the A549 cells. The comparison also revealed 24 and 10 cell line‐specific phospholipids in the PC9 and A549 cells, respectively. Given the demonstrated rapid enrichment and unambiguous identification of phospholipids at cellular levels, the developed approach can provide systematic profiling to study the under‐explored phospholipid species. [ABSTRACT FROM AUTHOR]

The oxygen‐stable state of the [Fe,Fe] hydrogenase H‐cluster is modeled. Insights into properties of the enzymatic oxygen‐stable state, and key factors governing deactivation and reactivation mechanism are elucidated. For details see the Research Article (e202408142) by Yih‐Chern Horng, Ming‐Hsi Chiang et al...By Yu‐Chiao Liu; Kai‐Ti Chu; Hong‐Ru Wang; Gene‐Hsiang Lee; Mei‐Chun Tseng; Cheng‐Hsin Wang; Yih‐Chern Horng and Ming‐Hsi ChiangReported by Author; Author; Author; Author; Author; Author; Author; Author [Extracted from the article]

The oxygen‐stable state of the [Fe,Fe] hydrogenase H‐cluster is modeled. Insights into properties of the enzymatic oxygen‐stable state, and key factors governing deactivation and reactivation mechanism are elucidated. For details see the Research Article (e202408142) by Yih‐Chern Horng, Ming‐Hsi Chiang et al...By Yu‐Chiao Liu; Kai‐Ti Chu; Hong‐Ru Wang; Gene‐Hsiang Lee; Mei‐Chun Tseng; Cheng‐Hsin Wang; Yih‐Chern Horng and Ming‐Hsi ChiangReported by Author; Author; Author; Author; Author; Author; Author; Author [Extracted from the article]

Two structurally simple Pt(II)‐directed self‐assembly loop complexes were prepared by reactions of cis‐(PEt3)2Pt(OTf)2 and the corresponding pyridylamide‐functionalized pyridyl ligands. Both Pt(II)‐based complexes exhibit singlet fluorescence, indicating that the platinum metal serves only as a structural, rather than a direct photophysical role within the loop framework. The crystal structure of complex 1 shows a distorted loop conformation with a hydrophobic pocket defined by the bridging ligands. The anion binding affinities of these two complexes were investigated with a range of anions. Such studies using UV–vis absorption, fluorescence, and 1H NMR titrations showed that complex 1 exhibits excellent binding sensitivity and selectivity for benzoate over acetate in solution via a combination of electrostatic, hydrogen‐bonding, and π–π interactions, whereas complex 2 shows comparable binding affinities toward acetate and benzoate due to the lack of favorable aromatic π–π interaction. [ABSTRACT FROM AUTHOR]