Organoplatinum‐Bridged Cyclotribenzylene Dimers Zhang, Jing; Aribot, Frédéric; Chambron, Jean‐Claude ...
European journal of inorganic chemistry,
September 1, 2023, 2023-09-00, 20230901, 2023-09, Letnik:
26, Številka:
25
Journal Article
Recenzirano
Odprti dostop
Cyclotribenzylenes (CTBs) combining carbonitrile (−CN) and alkyne (−C2H) substituents were synthesized as racemic mixtures and resolved by HPLC on chiral stationary phases. Two of these compounds ...were used to prepare platinum‐bridged CTB dimers, in which PtII is bound to the CTBs via Pt−alkynyl bonds in cis configuration. The organometallic complexes were examined by mass spectrometry and NMR spectroscopy, which indicated that they were obtained as mixtures of diastereoisomers (a meso or syn form and a pair of chiral or anti forms) when racemic CTBs were used. Enantiomerically pure complexes were prepared from resolved CTBs, which allowed us to distinguish the NMR signals of the chiral and meso forms in the diastereoisomeric mixtures. In certain conditions, the platinum complexes played the role of a pincer π‐alkynyl ligand for Cu(I) coming from the copper iodide used as a synthetic auxiliary. The Cu+ cations could be easily removed by treatment with NaCN, affording the mononuclear bis‐cyclotribenzylene complexes. These compounds failed to lead to metallo‐cryptophanes by coordination of two M(dppp)2+ complex subunits (M=Pd, Pt; dppp=1,3‐bis(diphenylphosphino)propane), each to two carbonitrile substituents belonging to different CTBs, pointing to the superiority of the one pot self‐assembly processes for the preparation of metallo‐cryptophanes.
Asymmetric cyclotribenzylenes (CTBs) incorporating an alkynyl and two nitrile functions were reacted with cis‐PtL2Cl2 (L=PEt3 or L2=1,3‐bis(diphenylphosphino)propane) to afford Pt‐bridged CTB dimers. When CuI was used as synthetic auxiliary, (Pt, Cu) binuclear complexes in which a CuCl/CuI moiety was π‐coordinated to the platinum‐bound bis‐alkynyl pincer, were also isolated. However, 1 : 2 reaction of the mononuclear CTB dimers with ML22+ did not generate metallocryptophanes.
The hyphenation of capillary electrophoresis and mass spectrometry (CE/MS) remains a minor technique compared with liquid chromatography/mass spectrometry (LC/MS), which represents nowadays the ...standard instrumentation, regardless of its introduction thirty years ago. However, from a theoretical point of view, CE coupling should be quite favorable especially with electrospray ionization mass spectrometry (ESI‐MS). At the time, the sensitivity provided by CE/MS was often limited, due to hyphenation requirements, which at some point appeared to disqualify CE/MS from benefiting from the performance gain driving the evolution of MS instruments. However, this context has been significantly modified in a matter of a few years. The development of innovative CE/MS interfacing systems has enabled an important improvement regarding sensitivity and reinforced robustness in order to provide an instrumentation accessible to the largest scientific community. Because of the unique selectivity delivered by the electrophoretic separation, CE/MS has proved to be particularly relevant for the analysis of biological molecules. The conjunction of these aspects is motivating the interest in CE/MS analysis and shows that CE/MS is mature enough to enrich the toolbox of analytical techniques for the analysis of complex biological samples. Here we discuss the characteristics of the major types of high‐sensitivity CE/ESI‐MS instrumentation and emphasize the late evolution and future positioning of CE/MS analysis for the characterization of biological molecules like peptides and proteins, through some pertinent applications.
Chiral gold(I) acetylide trinuclear complexes 1–3 based on the cyclotribenzylene platform and terminal PR3 ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission ...studied. They exhibited long‐lived blue phosphorescence in CHCl3 and a weak fluorescence in the UV. In MeOH/CHCl3 mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30–80 nm. The green emission observed in MeOH‐rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac‐1, suggesting that the latter is a true racemate.
Alkynylgold(I) C3‐symmetric complexes bearing triphenyl (1) and trialkyl phosphine ligands (2 and 3) were synthesized and studied. In CHCl3/MeOH mixtures 1 and 2 showed an AIE effect at 540 nm, probably originating from aurophilic interactions. 3 showed AIE only in nearly pure MeOH and in the solid state. The aggregation of optically pure 1 started at lower MeOH content than (±)‐1, indicating that the latter gave racemates rather than conglomerates.
The nuclear coactivator binding domain (NCBD) of transcriptional co‐regulator CREB‐binding protein (CBP) is an example of conformationally malleable proteins that can bind to structurally unrelated ...protein targets and adopt distinct folds in the respective protein complexes. Here, we show that the folding landscape of NCBD contains an alternative pathway that results in protein aggregation and self‐assembly into amyloid fibers. The initial steps of such protein misfolding are driven by intermolecular interactions of its N‐terminal α‐helix bringing multiple NCBD molecules into contact. These oligomers then undergo slow but progressive interconversion into β‐sheet‐containing aggregates. To reveal the concealed aggregation potential of NCBD we used a chemically synthesized mirror‐image d‐NCBD form. The addition of d‐NCBD promoted self‐assembly into amyloid precipitates presumably due to formation of thermodynamically more stable racemic β‐sheet structures. The unexpected aggregation of NCBD needs to be taken into consideration given the multitude of protein–protein interactions and resulting biological functions mediated by CBP.
Self assembled with a mirror: The self‐assembly of nuclear coactivator binding domain (NCBD) into oligomers and amyloid fibers is reported. The initial oligomerization is mediated through an N‐terminal helical fragment. Subsequently, the oligomers interconvert towards more stable β‐sheet structures through a process that is facilitated by the presence of a mirror‐image d‐NCBD construct.
Over the past decade there has been a growing interest in RNA modification analysis. High performance liquid chromatography–tandem mass spectrometry coupling (HPLC–MS/MS) is classically used to ...characterize post-transcriptional modifications of ribonucleic acids (RNAs). Here we propose a novel and simple workflow based on capillary zone electrophoresis–tandem mass spectrometry (CE–MS/MS), in positive mode, to characterize RNA modifications at nucleoside and oligonucleotide levels. By first totally digesting the purified RNA, prior to CE–MS/MS analysis, we were able to identify the nucleoside modifications. Then, using a bottom-up approach, sequencing of the RNAs and mapping of the modifications were performed. Sequence coverages from 68% to 97% were obtained for four tRNAs. Furthermore, unambiguous identification and mapping of several modifications were achieved.
Cyclotricyanobenzylene (CTB) 1 was resolved by HPLC on chiral stationary phase and the absolute configurations of its enantiomers were determined. Optically‐active pallado‐ and platinocryptophanes ...assembled separately from (+)‐1 and (–)‐1, and the optical properties of M3(dppp)3((+)‐1)2(OTf)6 and M3(dppp)3((–)‐1)2(OTf)6 (M = Pd and Pt; dppp = 1,3‐bis(diphenylphosphanyl)propane) were studied by polarimetry and electronic circular dichroism (ECD). The enantiomerization barriers of the metallocryptophanes depend only weakly on the nature of the metal. TD‐DFT calculations demonstrated the occurence of induced ECD effects from the optically active CTB 1 to the metal complex fragments. Comparison of the 1H NMR spectra of the optically‐pure and racemic metallocryptophanes confirmed that the latter formed diastereoselectively and enantioselectively. Self‐assembly of metallocryptophanes from two different CTBs (1 and 2) gave clear evidence of chemoselectivity for the process, using 1H NMR spectroscopy and ESI‐MS.
Metallocryptophanes were assembled from optically pure cyclotricyanotribenzylene (CTB) 1 and M(dppp)(OTf)2 (M = Pd and Pt), and their chiroptical properties were studied experimentally and theoretically, providing evidence of ICD effects. As shown by 1H NMR spectroscopy and ESI mass spectrometry, the reaction proceeds stereoselectively and chemoselectively when a second CTB is involved in the self‐assembly.
Chiral gold(I) acetylide trinuclear complexes 1-3 based on the cyclotribenzylene platform and terminal PR
ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission ...studied. They exhibited long-lived blue phosphorescence in CHCl
and a weak fluorescence in the UV. In MeOH/CHCl
mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30-80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac-1, suggesting that the latter is a true racemate.
•We highlight the relevance of CE as a reference method for mAbs and related product characterization.•We review CE-based methods as CGE, cIEF, icIEF and CZE for the characterization of mAbs and ...related product.•We highlight CE–MS coupling as future very relevant analytical tool for mAbs characterization.
Out of all categories, monoclonal antibodies (mAbs), biosimilar, antibody-drug conjugates (ADCs) and Fc-fusion proteins attract the most interest due to their strong therapeutic potency and specificity. Because of their intrinsic complexity due to a large number of micro-heterogeneities, there is a crucial need of analytical methods to provide comprehensive in-depth characterization of these molecules. CE presents some obvious benefits as high resolution separation and miniaturized format to be widely applied to the analysis of biopharmaceuticals. CE is an effective method for the separation of proteins at different levels. capillary gel electrophoresis (CGE), capillary isoelectric focusing (cIEF) and capillary zone electrophoresis (CZE) have been particularly relevant for the characterization of size and charge variants of intact and reduced mAbs, while CE–MS appears to be a promising analytical tool to assess the primary structure of mAbs and related products. This review will be dedicated to detail the current and state-of-the-art CE-based methods for the characterization of mAbs and related products.
A series of cyclopeptoid‐based iminosugar clusters has been evaluated to finely probe the ligand content‐dependent increase in α‐mannosidase inhibition. This study led to the largest binding ...enhancement ever reported for an enzyme inhibitor (up to 4700‐fold on a valency‐corrected basis), which represents a substantial advance over the multivalent glycosidase inhibitors previously reported. Electron microscopy imaging and analytical data support, for the best multivalent effects, the formation of a strong chelate complex in which two mannosidase molecules are cross‐linked by one inhibitor.
Breaking sweet records! Cyclopeptoid‐based iminosugar clusters (see figure) show the largest multivalent effects ever reported in glycosidase inhibition (up to 4700‐fold on a valency‐corrected basis). Electron microscopy imaging and analytical data support the formation of sandwich‐type complexes in which two mannosidase molecules are cross‐linked by one inhibitor.
Antibody-drug conjugates (ADCs) represent a fast growing class of biotherapeutic products. Their production leads to a distribution of species exhibiting different number of conjugated drugs ...overlaying the inherent complexity resulting from the monoclonal antibody format, such as glycoforms. ADCs require an additional level of characterization compared to first generation of biotherapeutics obtained through multiple analytical techniques for complete structure assessment. We report the development of complementary approaches implementing sheathless capillary electrophoresis-mass spectrometry (sheathless CE-MS) to characterize the different aspects defining the structure of brentuximab vedotin. Native MS using sheathless CE-MS instrument as a nanoESI infusion platform enabled accurate mass measurements and estimation of the average drug to antibody ratio alongside to drug load distribution. Middle-up analysis performed after limited IdeS proteolysis allowed to study independently the light chain, Fab and F(ab')2 subunits incorporating 1, 0 to 4 and 0 to 8 payloads respectively. Finally, a CZE-ESI-MS/MS methodology was developed in order to be compatible with hydrophobic drug composing ADCs. From a single injection, complete sequence coverage could be achieved. Using the same dataset, glycosylation and drug-loaded peptides could be simultaneously identified revealing robust information regarding their respective localization and abundance. Drug-loaded peptide fragmentation mass spectra study demonstrated drug specific fragments reinforcing identification confidence, undescribed so far. Results reveal the method ability to characterize ADCs primary structure in a comprehensive manner while reducing tremendously the number of experiments required. Data generated showed that sheathless CZE-ESI-MS/MS characteristics position the methodology developed as a relevant alternative for comprehensive multilevel characterization of these complex biomolecules.
Display omitted
•We confirm the power of sheathless CE/MS coupling for the characterization of ADC.•We demonstrate structural information of Lc, Fab and F(ab')2 subunits incorporating various number of drugs.•We determine the average Drug to antibody ratio (DAR).•We characterize unambiguously the drug-loaded-peptides with seven new diagnostic ions.
PDF
