Alpha‐1 antitrypsin variants in plasma from HIV‐infected patients revealed by proteomic and glycoproteomic analysis

Novel tools are necessary to explore proteins related to human immunodeficiency virus (HIV) infection. In this work, proteomic and glycoproteomic technology were employed to examine plasma samples from HIV‐positive patients. Through comparative proteome analysis of normal and HIV‐positive plasma samples, 19 differentially expressed protein spots related to 12 non‐redundant proteins were identified by ESI‐ion trap MS. Among these, the 130‐kDa isoform of α‐1‐antitrypsin was found to be decreased in HIV‐positive patients while another variant with a molecular weight of 40 kDa was increased. SWISS‐2‐D‐PAGE reference gel and protein sequence comparisons of the 40‐kDa protein showed homology with α‐1‐antitrypsin minus the N‐terminus, and its identity was further confirmed by 1‐D Western blotting and glycoproteomic analysis. In all, our results showed that proteomics and glycoproteomics are powerful tools for discovering proteins related to HIV infection. Furthermore, this 40‐kDa variant of α‐1‐antitrypsin found in the plasma of HIV‐positive individuals may prove to be a potentially useful biomarker for anti‐HIV research according to bioinformatics analysis.     

Screening and separation of α‐amylase inhibitors from Solanum nigrum with amylase‐functionalized magnetic graphene oxide combined with high‐speed counter‐current chromatography

A screening method using α‐amylase‐functionalized magnetic graphene oxide combined with high‐speed counter‐current chromatography was proposed and utilized to screen and separate α‐amylase inhibitors from extract of Solanum nigrum . The α‐amylase‐functionalized magnetic graphene oxide was characterized and found to demonstrate satisfactory structure, magnetic response (24.5 emu/g), and reusability (retained 90% of initial activity after five cycles). The conditions for the screening with α‐amylase functionalized magnetic graphene oxide were optimized and set at pH 7.0 and 25°C. As a result, two potent flavonoid compounds, apigenin‐7‐O‐glucuronide ( 1 ) and astragalin ( 2 ), were separated and collected through high‐speed counter‐current chromatography and subjected to high‐performance liquid chromatography analysis with purity higher than 90% (according to HPLC data), which were identified as α‐amylase inhibitors. These results suggested that utilization of α‐amylase functionalized magnetic graphene oxide in the rapid screening and isolation bioactive compounds from complex natural products is a feasible and environmentally friendly method.     

Palladium‐Catalyzed Oxidative Difunctionalization of Alkenes with α‐Carbonyl Alkyl Bromides Initiated through a Heck‐type Insertion: A Route to Indolin‐2‐ones

The oxidative interception of various σ‐alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium‐catalyzed oxidative difunctionalization reaction of alkenes with α‐carbonyl alkyl bromides is described, in which the σ‐alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp²)? H bond. This method can be applied to various α‐carbonyl alkyl bromides, including primary, secondary, and tertiary α‐bromoalkyl esters, ketones, and amides.     

Facile Solid‐Phase Organic Synthesis of 5‐Vinyl‐Substituted 1,2,4‐Oxadiazoles from Polymer‐Bound α‐Selenopropionic Acid

Cyclocondensation of polystyrene‐supported α‐selenopropionic acid with amidoximes in the presence of 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride (EDC) followed by oxidative deselenation efficiently afforded 5‐vinyl 1,2,4‐oxadiazoles in good yield and purity with a facile work‐up procedure.     

Screening and identification of α‐glucosidase inhibitors from Shenqi Jiangtang Granule by ultrafiltration liquid chromatography and mass spectrometry

Shenqi Jiangtang Granule, a well‐known traditional Chinese herbal preparation, has been widely used for the treatment of type II diabetes mellitus. In this work, an ultrafiltration liquid chromatography with quadrupole time‐of‐flight mass spectrometry method was proposed for the rapid identification of bioactive ingredients from Shenqi Jiangtang Granule using α‐glucosidase as an example. First, the chemical profile of this preparation was clarified, including 37 saponins, 17 flavonoids, 37 lignans, and seven other compounds. After incubation with α‐glucosidase in vitro, the methanol extract with an IC₅₀ value of 0.19 mg/mL exhibited significant inhibitory activity. Then, 18 specific binding peaks were screened, and 15 peaks were identified. Among these, ten compounds were reported to have potential α‐glucosidase inhibitory activity for the first time. Subsequently, the inhibitory activities of these active compounds were evaluated by ultraviolet spectrophotometry with p‐nitrophenyl α‐d‐ glucopyranoside as a substrate. As a result, gomisin J and gomisin D exhibited stronger α‐glucosidase inhibitory activities than other active compounds with IC₅₀ values of 77.69 and 133.85 μM, respectively. The results demonstrated that the integrated ultrafiltration liquid chromatography with mass spectrometry method was an effective and powerful tool for the discovery of active ingredients in Shenqi Jiangtang Granule.     

Alpha‐Helical Fragaceatoxin C Nanopore Engineered for Double‐Stranded and Single‐Stranded Nucleic Acid Analysis

Nanopores are used in single‐molecule DNA analysis and sequencing. Herein, we show that Fragaceatoxin C (FraC), an α‐helical pore‐forming toxin from an actinoporin protein family, can be reconstituted in sphingomyelin‐free standard planar lipid bilayers. We engineered FraC for DNA analysis and show that the funnel‐shaped geometry allows tight wrapping around single‐stranded DNA (ssDNA), resolving between homopolymeric C, T, and A polynucleotide stretches. Remarkably, despite the 1.2 nm internal constriction of FraC, double‐stranded DNA (dsDNA) can translocate through the nanopore at high applied potentials, presumably through the deformation of the α‐helical transmembrane region of the pore. Therefore, FraC nanopores might be used in DNA sequencing and dsDNA analysis.     

Expedient Synthesis of Ketones via N‐Heterocyclic Carbene/Nickel‐Catalyzed Redox‐Economical Coupling of Alcohols and Alkynes†

An N‐heterocyclic carbene/nickel‐catalyzed direct coupling of alcohols and internal alkynes to form α‐branched ketones has been developed. This methodology provides a new approach to afford branched ketones, which are difficult to access through the hydroacylation of simple internal alkenes with aldehydes. This redox‐neutral and redox‐economical coupling is free from any oxidative or reductive additives as well as stoichiometric byproducts. These reactions convert both benzylic and aliphatic alcohols and alkynes, two basic feedstock chemicals, into various α‐branched ketones in a single chemical step.     

Nickel‐Catalyzed α‐Arylation of Ketones with Phenol Derivatives

The nickel‐catalyzed α‐arylation of ketones with readily available phenol derivatives (esters and carbamates) provides access to useful α‐arylketones. For this transformation, 3,4‐bis(dicyclohexylphosphino)thiophene (dcypt) was identified as a new, enabling, air‐stable ligand for this transformation. The intermediate of an assumed C? O oxidative addition was isolated and characterized by X‐ray crystal‐structure analysis.     

Effects of covalent modification by 4‐hydroxy‐2‐nonenal on the noncovalent oligomerization of ubiquitin

When lipid membranes containing ω‐6 polyunsaturated fatty acyl chains are subjected to oxidative stress, one of the reaction products is 4‐hydroxy‐2‐nonenal (HNE)—a chemically reactive short chain alkenal that can covalently modify proteins. The ubiquitin proteasome system is involved in the clearing of proteins modified by oxidation products such as HNE, but the chemical structure, stability and function of ubiquitin may be impaired by HNE modification. To evaluate this possibility, the susceptibility of ubiquitin to modification by HNE has been characterized over a range of concentrations where ubiquitin forms non‐covalent oligomers. Results indicate that HNE modifies ubiquitin at only two of the many possible sites, and that HNE modification at these two sites alters the ubiquitin oligomerization equilibrium. These results suggest that any role ubiquitin may have in clearing proteins damaged by oxidative stress may itself be impaired by oxidative lipid degradation products. Copyright © 2016 John Wiley & Sons, Ltd.     

Combination of ultracentrifugation and solid‐phase extraction with subsequent chromatographic analysis of α‐tocopherol in erythrocyte membranes

A novel and rapid sample pretreatment technique based on a combination of ultracentrifugation and solid‐phase extraction for the determination of α‐tocopherol in human erythrocyte membranes by high‐performance liquid chromatography with ultraviolet detection is presented in this work. Red blood cell samples were ultracentrifuged (288 000 × g, 3 min, 4°C) in the presence of d ‐mannitol, 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid and calcium chloride. The α‐tocopherol was then extracted from the erythrocyte membranes by solid‐phase extraction with n‐hexane in the presence of ascorbic acid. Tocopherol acetate was used as the internal standard. The extract was dissolved in methanol and separated on the monolithic column Chromolith Performance RP‐18e (100 × 4.6 mm) using 100% methanol as the mobile phase. The absorbance of α‐tocopherol was measured at a wavelength of 295 nm. The method was validated and showed sufficient accuracy and precision, ranging from 96.4 to 100.8% and from 4.5 to 6.3%, respectively. Moreover, the developed method was applied to the determination of erythrocyte α‐tocopherol in real samples from patients. The combined ultracentrifugation and solid‐phase extraction technique substantially decreased the time for the sample pretreatment step compared to liquid–liquid extraction and could be applicable for the quantitation of other analytes in erythrocyte membranes.     

Rationally Designed α‐Helical Broad‐Spectrum Antimicrobial Peptides with Idealized Facial Amphiphilicity

A series of 12‐amino acid peptide analogs is designed using point mutation strategy based on an α‐helical peptide template. The first mutation in the series, KL12, has an idealized facial amphiphilicity. Subsequent mutations are performed to increase hydrophobic or cationic contents. Idealized facial amphiphilicity show enhanced antimicrobial activity and selectivity against most of the tested microbes. Increasing hydrophobic contents further enhance antimicrobial potency; however, selectivity of the most hydrophobic analog is impaired due to non‐specific interactions with mammalian cell membrane. This study demonstrates that facial amphiphilicity and hydrophobic content are strongly correlated with antimicrobial activity and selectivity of antimicrobial peptides.     

Efficient Synthesis of Differentiated syn‐1,2‐Diol Derivatives by Asymmetric Transfer Hydrogenation–Dynamic Kinetic Resolution of α‐Alkoxy‐Substituted β‐Ketoesters

Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α‐alkoxy‐β‐ketoesters in the presence of well‐defined, commercially available, chiral catalyst Ru^II–(N‐p‐toluenesulfonyl‐1,2‐diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of Ru^II‐ and Rh^III‐tethered precatalysts extended this process to more‐challenging substrates that bore alkenyl‐, alkynyl‐, and alkyl substituents to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)‐2‐ethoxy‐3‐(4‐hydroxyphenyl)‐propanoate, which is an important pharmacophore in a number of peroxisome proliferator‐activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type‐II diabetes.     

Synthesis,characterization and α‐amylase and α‐glucosidase inhibition studies of novel vanadyl chalcone complexes

A series of chalcone ligands and their corresponding vanadyl complexes of composition [VO (L^I–IV)₂(H₂O)₂]SO₄ (where L^I = 1,3‐Diphenylprop‐2‐en‐1‐one, L^II = 3‐(2‐Hydroxy‐phenyl)‐1‐phenyl‐propenone, L^III = 3‐(3‐Nitro‐phenyl)‐1‐phenyl‐propenone, L^IV = 3‐(4‐Methoxy‐phenyl)‐1‐phenyl‐propenone) have been synthesized and characterized using various spectroscopic (Fourier‐transform infrared, electrospray ionization mass, nuclear magnetic resonance, electron paramagnetic resonance, thermogravimetric analysis, vibrating sample magnetometer) and physico‐analytic techniques. Antidiabetic activities of synthesized complexes along with chalcones were evaluated by performing in vitro and in silico α‐amylase and α‐glucosidase inhibition studies. The obtained results displayed moderate to significant inhibition activity against both the enzymes by vanadyl chalcone complexes. The most potent complexes were further investigated for the enzyme kinetic studies and displayed the mixed inhibition for both the enzymes. Further, antioxidant activity of vanadyl chalcone complexes was evaluated for their efficiency to release oxidative stress using 2,2‐diphenyl‐1‐picryl‐hydrazyl‐hydrate assay, and two complexes (Complexes 2 and 4 ) have demonstrated remarkable antioxidant activity. All the complexes were found to possess promising antidiabetic and antioxidant potential.     

Synthesis and characterization of copolyperoxides of indene with styrene, α‐methylstyrene,and α‐phenylstyrene

The oxidative copolymerization of indene with styrene, α‐methylstyrene, and α‐phenylstyrene is investigated. Copolyperoxides of different compositions have been synthesized by the free‐radical‐initiated oxidative copolymerization of indene with vinyl monomers. The compositions of the copolyperoxides obtained from the ¹H and ¹³C NMR spectra have been used to determine the reactivity ratios of the monomers. The reactivity ratios indicate that indene forms an ideal copolyperoxide with styrene and α‐methylstyrene and alternating copolyperoxides with α‐phenylstyrene. Thermal degradation studies via differential scanning calorimetry and electron‐impact mass spectroscopy support the alternating peroxide units in the copolyperoxide chain. The activation energy for thermal degradation suggests that the degradation is dependent on the dissociation of the peroxide (? O? O? ) bonds in the backbone of the copolyperoxide chain. Their flexibility has been examined in terms of the glass‐transition temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2004–2017, 2002     

Unusual Cyclodextrin Derivatives as a New Avenue to Modulate Self‐ and Metal‐Induced Aβ Aggregation

Mounting evidence suggests an important role of cyclodextrins in providing protection in neurodegenerative disorders. Metal dyshomeostasis is reported to be a pathogenic factor in neurodegeneration because it could be responsible for damage involving oxidative stress and protein aggregation. As such, metal ions represent an effective target. To improve the metal‐binding ability of cyclodextrin, we synthesized three new 8‐hydroxyquinoline‐cyclodextrin conjugates with difunctionalized cyclodextrins. In particular, the 3‐difunctionalized regioisomer represents the first example of cyclodextrin with two pendants at the secondary rim, resulting in a promising compound. The derivatives have significant antioxidant capacity and the powerful activity in inhibiting self‐induced amyloid‐β aggregation seems to be led by synergistic effects of both cyclodextrin and hydroxyquinoline. Moreover, the derivatives are also able to complex metal ions and to inhibit metal‐induced protein aggregation. Therefore, these compounds could have potential as therapeutic agents in diseases related to protein aggregation and metal dyshomeostasis.     

Ru‐Catalyzed Decarboxylative Annulations of α‐Keto Acids with Internal Alkynes: Dual Roles of COOH as Directing Group and Leaving Group

Carboxylic acid serving as both directing and leaving group was discovered in Ru‐catalyzed decarboxylative annulations of α‐keto acids with alkynes. The well‐established protocol showed high functional group tolerance, which provided an efficient and alternative route to the coumarone backbone.     

An Amphipathic Alpha‐Helix Guides Maturation of the Ribosomally‐Synthesized Lipolanthines

The recently discovered strongly anti‐Gram‐positive lipolanthines represent a new group of lipidated, ribosomally synthesized and post‐translationally modified peptides (RiPPs). They are bicyclic octapeptides with a central quaternary carbon atom (avionin), which is installed through the cooperative action of the class‐III lanthipeptide synthetase MicKC and the cysteine decarboxylase MicD. Genome mining efforts indicate a widespread distribution and unprecedented biosynthetic diversity of lipolanthine gene clusters, combining elements of RiPPs, polyketide and non‐ribosomal peptide biosynthesis. Utilizing NMR spectroscopy, we show that a (θxx)θxxθxxθ (θ=L, I, V, M or T) motif, which is conserved in the leader peptides of all class‐III and ‐IV lanthipeptides, forms an amphipathic α‐helix in MicA that destines the peptide substrate for enzymatic processing. Our results provide general rules of substrate recruitment and enzymatic regulation during lipolanthine maturation. These insights will facilitate future efforts to rationally design new lanthipeptide scaffolds with antibacterial potency.     

Selective α‐Oxyamination and Hydroxylation of Aliphatic Amides

Compared to the α‐functionalization of aldehydes, ketones, even esters, the direct α‐modification of amides is still a challenge because of the low acidity of α‐CH groups. The α‐functionalization of N−H (primary and secondary) amides, containing both an unactived α‐C−H bond and a competitively active N−H bond, remains elusive. Shown herein is the general and efficient oxidative α‐oxyamination and hydroxylation of aliphatic amides including secondary N−H amides. This transition‐metal‐free chemistry with high chemoselectivity provides an efficient approach to α‐hydroxy amides. This oxidative protocol significantly enables the selective functionalization of inert α‐C−H bonds with the complete preservation of active N−H bond.     

Analysis of α‐acyloxyhydroperoxy aldehydes with electrospray ionization–tandem mass spectrometry (ESI‐MSn)

A series of α‐acyloxyhydroperoxy aldehydes was analyzed with direct infusion electrospray ionization tandem mass spectrometry (ESI/MSⁿ) as well as liquid chromatography coupled with the mass spectrometry (LC/MS). Standards of α‐acyloxyhydroperoxy aldehydes were prepared by liquid‐phase ozonolysis of cyclohexene in the presence of carboxylic acids. Stabilized Criegee intermediate (SCI), a by‐product of the ozone attack on the cyclohexene double bond, reacted with the selected carboxylic acids (SCI scavengers) leading to the formation of α‐acyloxyhydroperoxy aldehydes. Ionization conditions were optimized. [M + H]⁺ ions were not formed in ESI; consequently, α‐acyloxyhydroperoxy aldehydes were identified as their ammonia adducts for the first time. On the other hand, atmospheric‐pressure chemical ionization has led to decomposition of the compounds of interest. Analysis of the mass spectra (MS² and MS³) of the [M + NH₄]⁺ ions allowed recognizing the fragmentation pathways, common for all of the compounds under study. In order to get detailed insights into the fragmentation mechanism, a number of isotopically labeled analogs were also studied. To confirm that the fragmentation mechanism allows predicting the mass spectrum of different α‐acyloxyhydroperoxy aldehydes, ozonolysis of α‐pinene, a very important secondary organic aerosol precursor, was carried out. Spectra of the two ammonium cationized α‐acyloxyhydroperoxy aldehydes prepared with α‐pinene, cis‐pinonic acid as well as pinic acid were predicted very accurately. Possible applications of the method developed for the analysis of α‐acyloxyhydroperoxy aldehydes in SOA samples, as well as other compounds containing hydroperoxide moiety are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Accurate identification of dimers from α‐pinene oxidation using high‐resolution collision‐induced dissociation mass spectrometry

Interest in mass spectrometry of highly oxidized dimers from α‐pinene oxidation has increased in the atmospheric chemistry field. Here, we apply high‐resolution collision‐induced dissociation mass spectrometry (HR‐CID‐MS) with an atmospheric pressure ionization source to investigate in detail how α‐pinene‐derived dimers are detected and identified by MS. The resulting HR‐CID spectra and specific fragmentation patterns suggest that a large fraction of dimer ions detected in full‐scan mass spectra can be hydrogen‐bonded artifact clusters and the residual small fraction includes covalently bonded actual dimers. We also show how individual fractions of the artifact clusters and actual dimers are calculated using the HR‐CID spectra.