Read by QxMD icon Read

Chemical Science

Siheng Li, Lin Wang, Fei Yu, Zhiling Zhu, Dema Shobaki, Haoqing Chen, Mu Wang, Jun Wang, Guoting Qin, Uriel J Erasquin, Li Ren, Yingjun Wang, Chengzhi Cai
We demonstrated that copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction could be performed inside live mammalian cells without using a chelating azide. Under optimized conditions, the reaction was performed in human ovary cancer cell line OVCAR5 in which newly synthesized proteins were metabolically modified with homopropargylglycine (HPG). This model system allowed us to estimate the efficiency of the reaction on the cell membranes and in the cytosol using mass spectrometry. We found that the reaction was greatly promoted by a tris(triazolylmethyl)amine Cu(I) ligand tethering a cell-penetrating peptide...
March 1, 2017: Chemical Science
Shouliang Yang, Kuppusamy Sankar, Colin K Skepper, Timothy J Barker, John C Lukesh, Daniel M Brody, Manuela M Brütsch, Dale L Boger
The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deep-seated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted alkenes were found to productively initiate the cycloaddition cascade with tethered electron-deficient 1,3,4-oxadiazoles...
February 1, 2017: Chemical Science
Qinsi Zheng, Steffen Jockusch, Zhou Zhou, Roger B Altman, Hong Zhao, Wesley Asher, Michael Holsey, Signe Mathiasen, Peter Geggier, Jonathan A Javitch, Scott C Blanchard
Bright, long-lasting organic fluorophores enable a broad range of imaging applications. "Self-healing" fluorophores, in which intra-molecularly linked protective agents quench photo-induced reactive species, exhibit both enhanced photostability and biological compatibility. However, the self-healing strategy has yet to achieve its predicted potential, particularly in the presence of ambient oxygen where live-cell imaging studies must often be performed. To identify key bottlenecks in this technology that can be used to guide further engineering developments, we synthesized a series of Cy5 derivatives linked to the protective agent cyclooctatetraene (COT) and examined the photophysical mechanisms curtailing their performance...
January 1, 2017: Chemical Science
Jimin P Kim, Zhiwei Xie, Michael Creer, Zhiwen Liu, Jian Yang
Chloride is an essential electrolyte that maintains homeostasis within the body, where abnormal chloride levels in biological fluids may indicate various diseases such as Cystic Fibrosis. However, current analytical solutions for chloride detection fail to meet the clinical needs of both high performance and low material or labor costs, hindering translation into clinical settings. Here we present a new class of fluorescence chloride sensors derived from a facile citrate -based synthesis platform that utilize dynamic quenching mechanisms...
January 1, 2017: Chemical Science
Goutham Kodali, Joshua A Mancini, Lee A Solomon, Tatiana V Episova, Nicholas Roach, Christopher J Hobbs, Pawel Wagner, Olga A Mass, Kunche Aravindu, Jonathan E Barnsley, Keith C Gordon, David L Officer, P Leslie Dutton, Christopher C Moser
Natural selection in photosynthesis has engineered tetrapyrrole based, nanometer scale, light harvesting and energy capture in light-induced charge separation. By designing and creating nanometer scale artificial light harvesting and charge separating proteins, we have the opportunity to reengineer and overcome the limitations of natural selection to extend energy capture to new wavelengths and to tailor efficient systems that better meet human as opposed to cellular energetic needs. While tetrapyrrole cofactor incorporation in natural proteins is complex and often assisted by accessory proteins for cofactor transport and insertion, artificial protein functionalization relies on a practical understanding of the basic physical chemistry of protein and cofactors that drive nanometer scale self-assembly...
January 1, 2017: Chemical Science
Robert A Craig, Jennifer L Roizen, Russell C Smith, Amanda C Jones, Scott C Virgil, Brian M Stoltz
An enantioselective and diastereoselective approach toward the synthesis of the polycyclic norditerpenoid ineleganolide is disclosed. A palladium-catalyzed enantioselective allylic alkylation is employed to stereoselectively construct the requisite chiral tertiary ether and facilitate the synthesis of a 1,3-cis-cyclopentenediol building block. Careful substrate design enabled the convergent assembly of the ineleganolide [6,7,5,5]-tetracyclic scaffold by a diastereoselective cyclopropanation-Cope rearrangement cascade under unusually mild conditions...
January 1, 2017: Chemical Science
Yang Li, Gao-Hui Pan, Ming Hu, Bang Liu, Ren-Jie Song, Jin-Heng Li
A new metal-free oxidative decarbonylative [2 + 2 + 2] carbocyclization of N-(2-ethynylaryl)acrylamides with tertiary and secondary alkyl aldehydes is described. This reaction enables the formation of three new C-C bonds in a single reaction by a sequence of oxidative decarbonylation, radical addition across C-C unsaturated bonds, C-H functionalization and annulation, and represents the first oxidative decarbonylative [2 + 2 + 2] carbocyclization approach using tertiary and secondary alkyl aldehydes as a two carbon unit for assembling six-membered carbocycle-fused polycycles...
December 14, 2016: Chemical Science
J Saska, W Lewis, R S Paton, R M Denton
We report a 12-step catalytic enantioselective formal synthesis of malhamensilipin A (3) and diastereoisomeric analogues from (E)-2-undecenal. The convergent synthesis relied upon iterative epoxidation and phosphorus(v)-mediated deoxydichlorination reactions as well a titanium-mediated epoxide-opening to construct the C11-C16 stereohexad. The latter transformation occurred with very high levels of stereoretention regardless of the C13 configuration of the parent epoxide, implicating anchimeric assistance of either the γ- or δ-chlorine atoms, and the formation of chloretanium or chlorolanium ions, respectively...
December 11, 2016: Chemical Science
Derek T Ahneman, Abigail G Doyle
We describe the functionalization of α-amino C-H bonds with aryl halides using a combination of nickel and photoredox catalysis. This direct C-H, C-X coupling uses inexpensive and readily available starting materials to generate benzylic amines, an important class of bioactive molecules. Mechanistically, this method features the direct arylation of α-amino radicals mediated by a nickel catalyst. This reactivity is demonstrated for a range of aryl halides and N-aryl amines, with orthogonal scope to existing C-H activation and photoredox methodologies...
December 1, 2016: Chemical Science
Dean H Barrett, Michael S Scurrell, Cristiane B Rodella, Beatriz Diaz, David G Billing, Paul J Franklyn
When Au is subdivided to the nanoscale its reactivity changes from an inert nature to one of incredible reactivity which is not replicated by other catalysts. When dispersed onto metal oxides such as TiO2, nano-Au has shown high reactivities for a multitude of reduction and oxidation reactions of industrial importance with potential and current uses such as, CO oxidation, NO x reduction, purification of hydrogen for fuel cells, water gas shift reactions, abatement of volatile organic compounds (VOC's) as well as pollution and emission control systems such as autocatalysts...
November 18, 2016: Chemical Science
Palapuravan Anees, Karivachery V Sudheesh, Purushothaman Jayamurthy, Arunkumar R Chandrika, Ramakrishnapillai V Omkumar, Ayyappanpillai Ajayaghosh
Accurate monitoring of pH variations inside cells is important for the early diagnosis of diseases such as cancer. Even though a variety of different pH sensors are available, construction of a custom-made sensor array for measuring minute variations in a narrow biological pH window, using easily available constituents, is a challenge. Here we report two-component hybrid sensors derived from a protein and organic dye nanoparticles whose sensitivity range can be tuned by choosing different ratios of the components, to monitor the minute pH variations in a given system...
November 18, 2016: Chemical Science
Jian-Siang Poh, Shing-Hing Lau, Iain G Dykes, Duc N Tran, Claudio Battilocchio, Steven V Ley
Here we report the in situ generation of transient allylic boronic species, by reacting TMSCHN2 and E-vinyl boronic acids, followed by their subsequent trapping with aldehydes as electrophiles to yield homoallylic alcohols. This metal-free reaction was initially discovered by the use of a flow chemistry approach to generate a variety of homoallylic alcohols in a straightforward fashion and then transferred to a batch protocol.
November 18, 2016: Chemical Science
A Singh, C J Fennell, J D Weaver
Photocatalytic alkene synthesis can involve electron and energy transfer processes. The structure of the photocatalyst can be used to control the rate of the energy transfer, providing a mechanistic handle over the two processes. Jointly considering catalyst volume and emissive energy provides a highly sensitive strategy for predicting which mechanistic pathway will dominate. This model was developed en route to a photocatalytic Caryl-F alkenylation reaction of alkynes and highly-fluorinated arenes as partners...
November 18, 2016: Chemical Science
Verena Pfeifer, Travis E Jones, Sabine Wrabetz, Cyriac Massué, Juan J Velasco Vélez, Rosa Arrigo, Michael Scherzer, Simone Piccinin, Michael Hävecker, Axel Knop-Gericke, Robert Schlögl
Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous Ir(III/IV) oxyhydroxides (IrO x ) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO2, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive species is not solely a property of the metal but is intimately tied to the electronic structure of oxygen. We use a combination of synchrotron-based X-ray photoemission and absorption spectroscopies, ab initio calculations, and microcalorimetry to show that holes in the O 2p states in amorphous IrO x give rise to a weakly bound oxygen that is extremely susceptible to nucleophilic attack, reacting stoichiometrically with CO already at room temperature...
November 18, 2016: Chemical Science
Jin Zhou, Huimin Ma
Correction for 'Design principles of spectroscopic probes for biological applications' by Jin Zhou et al., Chem. Sci., 2016, DOI: 10.1039/c6sc02500e.
October 19, 2016: Chemical Science
Adam J Jackson, Davide Tiana, Aron Walsh
Correction for 'A universal chemical potential for sulfur vapours' by Adam J. Jackson et al., Chem. Sci., 2016, 7, 1082-1092.
October 19, 2016: Chemical Science
Guo-Xing Li, Cristian A Morales-Rivera, Yaxin Wang, Fang Gao, Gang He, Peng Liu, Gong Chen
Correction for 'Photoredox-mediated Minisci C-H alkylation of N-heteroarenes using boronic acids and hypervalent iodine' by Guo-Xing Li et al., Chem. Sci., 2016, DOI: ; 10.1039/c6sc02653b.
October 19, 2016: Chemical Science
Changxing Qi, Jian Bao, Jianping Wang, Hucheng Zhu, Yongbo Xue, Xiaochuan Wang, Hua Li, Weiguang Sun, Weixi Gao, Yongji Lai, Jian-Guo Chen, Yonghui Zhang
Asperterpenes A (1) and B (2), two 3,5-dimethylorsellinic acid-based meroterpenoids that contain a unique β-oriented Me-21 with an unprecedented 1,2,5-trimethyl-4,9-dioxobicyclo[3.3.1]non-2-ene-3-carboxylic acid moiety, were obtained from Aspergillus terreus in very limited amounts of 3.6 mg and 1.8 mg, respectively. The absolute structure of 1 was determined using X-ray diffraction. Because of the low yield of 1, a comprehensive characterization of the BACE1 inhibitory activities of 1 was completed via molecular biological, cell and animal studies guided by in silico target confirmation (ISTC)...
October 19, 2016: Chemical Science
Aisling Byrne, Christopher S Burke, Tia E Keyes
Fluorescence microscopy has undergone a dramatic evolution over the past two decades with development of super-resolution far-field microscopy methods that break the light diffraction limited resolution of conventional microscopy, offering unprecedented opportunity to interrogate cellular processes at the nanoscale. However, these methods make special demands of the luminescent agents used for contrast and development of probes suited to super-resolution fluorescent methods is still relatively in its infancy...
October 19, 2016: Chemical Science
Sai-Ho Lee, Iain M Blake, Allan G Larsen, James A McDonald, Kei Ohkubo, Shunichi Fukuzumi, Jeffrey R Reimers, Maxwell J Crossley
Porphyrin-based photosynthetic reaction centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale...
October 19, 2016: Chemical Science
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"