Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy

Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z₄ + H]^+● fragment ion-radicals of the R-C^●H-CONH- type, initially formed by N?C_α bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [^●DAAR + H]⁺ isomers and used to assign structures to the action spectra. The potential energy surface of [^●DAAR + H]⁺ isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [^●XAAR + H]⁺ ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone C_α positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H]^●-ETD fragments containing Asp, Asn, Glu, and Gln residues.

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Triplet build in and decay of isolated polyspirobifluorene chains in dilute solution

The triplet kinetics of a conjugated polymer, polyspirobifluorene, have been studied using time resolved photoinduced absorption spectroscopy and gated emission delayed fluorescence. Working on isolated polymer chains in dilute solution, we pay particular attention to the buildup and decay of the triplet states following intersystem crossing from the excited singlet state. Confirmation of intersystem crossing as a monomolecular cold process has been made. At high excitation powers an initial fast decay of the triplet has been observed; this is attributed to intrachain triplet-triplet annihilation. From this observation we estimate the lower bound of the intersystem crossing yield as 1.2%. We also calculate the intrachain annihilation constant to be (2.9+/-0.1)x 10(8) cm(3) s(-1).     

Substituted metal carbonyls. Part 25: Unidentate,intramolecular, and intermolecular bridging modes of 1,1′-bis(diphenylphosphino)ferrocene inM 3S2(CO)9 (M = Fe,Ru) cluster derivatives

Carbonyl exchange of Fe₃(₃-S)₂(CO)₉ wioth1,1-bis(diphenylphosphino)ferrocene (dppf) in refluxing THF gives a cluster ligand with a pendant phosphine moiety, Fe₃(₃-S)₂(CO)₈ (gn¹-Ph₂PlC₅H₄)Fe(C₅H₄)P⁴ MePh₂)]1 ^–,4. Addition of 1 to AuCl(SMe₂) gives ClAu(-dppf) Fe₄(₃-S)₂(CO)₈,8 (45%). Spectroscopic evidence is also obtained for (OC)₈ (₃-S)₂Fe₃(-dppf) Os₃(CO)₁₁,7 and PdCl₂[(-dppf)Fe₃(₃-D)₂(CO)₈]₂,9, from1 and Os₃(CO)₁₁(CH₃CN) and PdCl₂CN)₂, respectively. Crystal data dor3: space group P2₁/n,a = 10.891(3) Å,b = 19.939(3) Å,c = 20.443(2) Å, 100.17(2)°.Z = 4, 3917 reflections,R = 0.049.     

Substituted metal carbonyls XXIII . Syntheses of unicoordinated diphosphine complexes of Cr and Mo and their entry into heterobimetallics MM′(CO)10(μ-P-P) [M, M′= Cr, Mo, W; P---P = Ph2P(CH2)nPPh2, n = 2–4] as metalloligands

A series of pentacarbonyl complexes of chromium and molybdenum with unicoordinated-diphosphines, M(CO)₅(η¹-P-P) (P-P = dppe, dppp, dppb) has been prepared by amine oxide-induced phosphine substitution of the binary carbonyls. The basicity of the pendant phosphine groups was demonstrated by their ready conversion to the diphosphine-bridged heterobimetallic complexes (OC)₅M(μ-P-P)M′(CO)₅ (M, M′= Cr, Mo, W; M ≠ M′) in the presence of MCO)₅(CH₃CN). The complexes were characterized by IR and NMR (¹H and ³¹P-{¹H}) spectroscopy.     

Comparative reactivity studies of dppf-containing CpRu and (C6Me6)Ru complexes towards different donor ligands (dppf=1,1-bis(diphenylphosphino)ferrocene)

[CpRu(dppf)Cl] (Cp=η⁵-C₅H₅) (1) and [(HMB)Ru(dppf)Cl]PF₆ ((HMB)=η⁶-C₆Me₆) (3) react with different donor ligands to give rise to N-, P- and S-bonded complexes. The stoichiometric reactions of 1 and 3 with NaNCS give the mononuclear complexes [CpRu(dppf)(NCS)] (2) and [(HMB)Ru(dppf)(NCS)]PF₆ (4), respectively, in yields above 80%, while 3 also gives a dppf-bridged diruthenium complex [(HMB)Ru(NCS)₂]₂(μ-dppf) (5) in 67% yield from reaction with four molar equivalents of NaNCS. Compound 5 is also obtained in 70% yield from the reaction of 4 with excess NaNCS. With CH₃CN in the presence of salts, both 1 and 3 give their analogous solvento derivatives [CpRu(dppf)(CH₃CN)]BPh₄ (6) and [(HMB)Ru(dppf)(CH₃CN)] (PF₆)₂ (7). With phosphines, the reaction of 1 gives chloro-displaced complexes [(CpRu(dppf)L]PF₆ (L =PMe₃ (8), PMe₂Ph(9)), whereas the reaction of 3 with PMe₂Ph leads to substitution of dppf, giving [(HMB)Ru(PMe₂Ph)₂Cl] PF₆ (10). The reaction of 1 with NaS₂CNEt₂ gives a dinuclear dppf-bridged complex [{CpRu(S₂CNEt₂)}₂(μ-dppf)] (11), whereas that of 3 results in loss of the HMB ligand giving a mononuclear complex [Ru(dppf)(S₂CNEt₂)₂] (12). With elemental sulfur S₈, 1 is oxidized to give a dinuclear CpRu^III dppf-chelated complex [{CpRu(dppf)}₂(μ-S₂)](BPh₄)Cl (13), whereas 3 undergoes oxidation at the ligand, giving a dppf-displaced complex [(HMB)Ru(CH₃CN)₂Cl]PF₆ (14) and free dppfS₂. The structures of 1, 2, 5-9, 11, 13 and 14 were established by X-ray single crystal diffraction analyses. Of these, 5 and 11 both contain a dppf-bridge between Ru^II centers, while 13 is a dinuclear CpRu^III disulfide-bridged complex; all the others are mononuclear. All complexes obtained were also spectroscopically characterized.     

常见翡翠的三维荧光光谱特征研究

翡翠为一种珍贵的玉石.不同品级的翡翠价值差异巨大,翡翠经充填、染色等处理以提高外观质量,并冒充天然翡翠.鉴别翡翠就显得非常必要.全面收集了市场上常见的A,B,C,不同颜色B+C货翡翠样品,在常规宝石学特征描述的基础上,进行了三维荧光光谱测试.三维荧光光谱技术是近年发展起来的一门新的荧光分析技术,该技术在宝石学方面还未得...     

High Throughput Isolation and Data Independent Acquisition Mass Spectrometry (DIA-MS) of Urinary Extracellular Vesicles to Improve Prostate Cancer Diagnosis

Proteomic profiling of extracellular vesicles (EVs) represents a promising approach for early detection and therapeutic monitoring of diseases such as cancer. The focus of this study was to apply robust EV isolation and subsequent data-independent acquisition mass spectrometry (DIA-MS) for urinary EV proteomics of prostate cancer and prostate inflammation patients. Urinary EVs were isolated by functionalized magnetic beads through chemical affinity on an automatic station, and EV proteins were analyzed by integrating three library-base analyses (Direct-DIA, GPF-DIA, and Fractionated DDA-base DIA) to improve the coverage and quantitation. We assessed the levels of urinary EV-associated proteins based on 40 samples consisting of 20 cases and 20 controls, where 18 EV proteins were identified to be differentiated in prostate cancer outcome, of which three (i.e., SERPINA3, LRG1, and SCGB3A1) were shown to be consistently upregulated. We also observed 6 out of the 18 (33%) EV proteins that had been developed as drug targets, while some of them showed protein-protein interactions. Moreover, the potential mechanistic pathways of 18 significantly different EV proteins were enriched in metabolic, immune, and inflammatory activities. These results showed consistency in an independent cohort with 20 participants. Using a random forest algorithm for classification assessment, including the identified EV proteins, we found that SERPINA3, LRG1, or SCGB3A1 add predictable value in addition to age, prostate size, body mass index (BMI), and prostate-specific antigen (PSA). In summary, the current study demonstrates a translational workflow to identify EV proteins as molecular markers to improve the clinical diagnosis of prostate cancer.