Local Structures and Chemical Properties of Deprotonated Arginine

The potential energy surface of gaseous deprotonated arginine has been systematically in- vestigated by first principles calculations. At the B3LYP/6-31G（d） level, apart from the identification of several stable local structures, a new global minimum is located which is about 6.56 k J/tool more stable than what has been reported. The deprotonated arginine molecule has two distinct forms with the deprotonation at the carboxylate group （COO-）. These two forms are bridged by a very high energy barrier and possess very different IR spectral profiles. Our calculated proton dissociation energy and gas-phase acidity of argi- nine molecule are found to be in good agreement with the corresponding experimental results. The predicted geometries, dipole moments, rotational constants, vertical ionization energies and IR spectra of low energy conformers will be useful for future experimental measurements.

Enabling high-efficiency ethanol oxidation on NiFe-LDH via deprotonation promotion and absorption inhibition

Nucleophile oxidation reaction(NOR), represented by ethanol oxidation reaction(EOR), is a promising pathway to replace oxygen evolution reaction(OER). EOR can effectively reduce the driving voltage of hydrogen production in direct water splitting. In this work, large current and high efficiency of EOR on a Ni, Fe layered double hydroxide(NiFe-LDH) catalyst were simultaneously achieved by a facile fluorination strategy. F in NiFe-LDH can reduce the activation energy of the dehydrogenation reaction, thus promoting the deprotonation process of NiFe-LDH to achieve a lower EOR onset potential. It also weakens the absorption of OH-and nucleophile electrooxidation products on the surface of NiFe-LDH at a higher potential, achieving a high current density and EOR selectivity, according to density functional theory calculations. Based on our experiment results, the optimized fluorinated NiFe-LDH catalyst achieves a low potential of 1.386 V to deliver a 10 mA cm^(-2)EOR. Moreover, the Faraday efficiency is greater than 95%, with a current density ranging from 10 to 250 mA cm^(-2). This work provides a promising pathway for an efficient and cost-effective NOR catalyst design for economic hydrogen production.

Experimental and Theoretical Study of Deprotonation of DNA Adenine Cation Radical

Among all the DNA components, extremely redox-active guanine （G） and adenine （A） bases are subject to facile loss of an electron and form cation radicals （G＋＂ and A＋＇） when exposed to irradiation or radical oxidants. The subsequent deprotonation of G＋＇ and A＋＇ can invoke DNA damage or interrupt hole transfer in DNA. However, compared with intensive reports for G＋, studies on the deprotonation of A＋ are still limited at present. Herein, we investigate the deprotonation behavior of A＋. by time-resolved laser flash photolysis. The deprotonation product of A（N6-H）＇ is observed and the deprotonation rate constant, （2.0±0.1）×10 7 s-1, is obtained at room temperature. Further, the deprotonation rate con- stants of A＋. are measured at temperatures varying from 280 K to 300 K, from which the activation energy for the N6-H deprotonation is determined to be （17.1±1.0） kJ/mol by Arrhenius equation. In addition, by incorporating the aqueous solvent effect, we perform density functional theory calculations for A＋ deprotonation in free base and in duplex DNA. Together with experimental results, the deprotonation mechanisms of A＋ in free base and in duplex DNA are revealed, which are of fundamental importance for understanding the oxidative DNA damage and designing DNA-based electrochemical devices.

Synthesis and Crystal Structure of 1,2-Bis-(p-nitrophenylsulfonamido)-4,5-dinitrobenzene

The title compound, 1,2-bis-（p-nitro-phenylsulfonamido）-4,5-dinitrobenzene, was synthesized and characterized by elemental analysis, IR and 1H NMR. A pale yellow prism crystal of C23H26N8O13S2 （Mr = 686.64） was obtained in DMF solution and determined by single-crystal X-ray diffraction method. It crystallizes in triclinic system, space group P1 with a = 10.346（4）, b = 12.210（5）, c = 12.976（5）A , α = 108.220（8）, β = 99.482（4）, γ = 95.490（4）°, V = 1516.7（10） A^3, Z = 2, Dc = 1.504 g/cm^3, F（000） = 712, μ = 0.254, Mr = 686.64, the final R = 0.0561 and wR = 0.1487. One sulfonamido group of the title compound is deprotoned and forms N（3）=C（13）. The crystal involves N,N-dimethylamine from the decomposition of DMF and the proton is transferred to N,N- dimethylamine. It is a strong proof for the characterization of deprotoned recognition compound by X-ray single-crystal structure.

Isomerization of Hydrofluorocyclopentenes Promoted by Fluoride Anion

The isomerization of hydrofluorocyclopentenes promoted by fluoride anion was investigated. It was found that two processes were responsible for interconversion of the isomers: an allylic syn-addition/elimination of fluoride anion that does not change the mutual positions of hydrogen atoms but is responsible for transfers of fluorine atoms, and a fluoride anion-assisted deprotonation/protonation which does not change the mutual positions of fluorine atoms but is responsible for transfers of hydrogen atoms. In the deprotonation, HF can easily capture excess fluoride anion to form HF2- anion which can probably inhibit the protonation.

Raman Spectra of 1,2,4-Triazole-3-carboxylate Solution

Raman spectra of 1,2,4-triazole-3-carboxylate (TC- anion) and its ring-deprotonated deriva- tive (dpTC2- dianion) in aqueous solutions were measured respectively. The density func- tional theory calculations were performed using MN15 functional and PCM solvent model to investigate their structures, as well as the vibrational frequencies and Raman intensi- ties. With the aid of the calculated spectra, all the observed Raman bands of dpTC2- were clearly assigned, with taking into account the deuteration shifts. Moreover, various protonic tautomers of TC- anion were compared in the present theoretical calculations, and 2H- tautomer was found more stable. The experimental Raman spectrum of TC- solution was roughly consistent with the calculated spectrum of the monomeric 2H-tautomer of TC-, but some splits existed for a few bands when compared to the calculated spectra, which might be contributed by the hydrogen-bonding dimers of TC-.

Theoretical Studies on Structural and Spectroscopic Properties of Photoelectrochemical Cell Ruthenium Sensitizers―the Derivatives of N3

A series of dye molecules was designed theoretically.Particularly,azoles and their derivatives were chosen as the modifying groups linking to ancillary ligands of [Ru（dcbpyH2）2（NCS）2]（N3,dcbpy=4,4＇-dicarboxy2,2＇-bipyridine;NCS=thiocyanato）.Density functional theory（DFT） based approaches were applied to exploring the electronic structures and properties of all these systems.The dye molecule with 1,2,4-triazole groups which exhibits a very high intensity of absorption in visible region,was obtained.Time-dependent DFT（TD-DFT） results indicate that the ancillary ligand dominates the molecular orbital（MO） energy levels and masters the absorption transition nature to a certain extent.The deprotonation of anchoring ligand not only affects the frontier MO energy levels but also controls the energy gaps of the highest occupied MO（HOMO） to the lowest unoccupied MO（LUMO） and LUMO to LUMO＋1 orbital.If the gap between LUMO-LUMO＋1 is small enough,the higher efficiency of dye-sensitized solar cell（DSSC） should be expected.

Molecular mechanism of base pairing infidelity during DNA duplication upon one-electron oxidation

The guanine radical cation(G?+)is formed by one-electron oxidation from its parent guanine(G).G?+is rapidly deprotonated in the aqueous phase resulting in the formation of the neutral guanine radical[G(-H)?].The loss of proton occurs at the N1 nitrogen,which is involved in the classical Watson-Crick base pairing with cytosine(C).Employing the density functional theory(DFT),it has been observed that a new shifted base pairing configuration is formed between G(-H)?and C constituting only two hydrogen bonds after deprotonation occurs.Using the DFT method,G(-H)?was paired with thymine(T),adenine(A)and G revealing substantial binding energies comparable to those of classical G-C and A-T base pairs.Hence,G(-H)?does not display any particular specificity for C compared to the other bases.Taking into account the long lifetime of the G(-H)?radical in the DNA helix(5 s)and the rapid duplication rate of DNA during mitosis/meiosis(5-500 bases per s),G(-H)?can pair promiscuously leading to errors in the duplication process.This scenario constitutes a new mechanism which explains how one-electron oxidation of the DNA double helix can lead to mutations.

Synchronous deprotonation–protonation for mechanically robust chitin/aramid nanofibers conductive aerogel with excellent pressure sensing, thermal management, and electromagnetic interference shielding

Aerogels with regularly porous structure and uniformly distributed conductive networks have received extensive attention in wearable electronic sensors,electromagnetic shielding,and so on.However,the poor mechanical properties of the emerging nanofibers-based aerogels are limited in practical applications.In this work,we developed a synchronous deprotonation–protonation method in the KOH/dimethyl sulfoxide(DMSO)system at room temperature for achieving chitin cross-linked aramid nanofibers(CANFs)rather than chitin nanofibers(ChNFs)and aramid nanofibers(ANFs)separately by using chitin and aramid pulp as raw materials.After freeze-drying process,the cross-linked chitin/aramid nanofibers(CA)aerogel exhibited the synergetic properties of ChNF and ANF by the dual-nanofiber compensation strategy.The mechanical stress of CA aerogel was 170 kPa at 80%compressive strain,increased by 750%compared with pure ChNF aerogel.Similarly,the compressibility of CA aerogel was somewhat improved compared to ANF aerogel.The enhancement verified that the crosslinking reaction between ANF and ChNF during the synchronous deprotonation process was formed.Afterwards,the conductive aerogels with uniform porous structure(CA-M)were successfully obtained by vacuum impregnating CA aerogels in Ti_(3)C_(2)T_(x) MXene solution,displaying low thermal conductivity(0.01 W/(m·K)),high electromagnetic interference(EMI)shielding effectiveness(SE)(75 dB),flame retardant,and heat insulation.Meanwhile,the as-obtained CA-M aerogels were also applied as a pressure sensor with excellent compression cycle stability and superior human motion monitoring capabilities.As a result,the dual-nanofiber based conductive aerogels have great potentials in flexible/wearable electronics,EMI shielding,flame retardant,and heat insulation.

Rhodium-catalyzed addition reactions of benzylic C–H bonds to cyclic N-sulfonyl ketimines viaπ-coordination

Mannich-type reactions are a widely used method for the synthesis of amines due to the readily availability of nucleophiles and electrophiles.However,the inclusion of alkylarenes instead of active carbon pronucleophiles such as aldehydes and ketones in these addition reactions has been a challenge due to the inherent difficulty of benzylic deprotonation.In this study,we present a novel approach for the construction of N-sulfonyl amines via rhodium-catalyzed addition of unbiased benzylic C–H bonds to cyclic N-sulfonyl ketamines throughπ-coordination.This strategy enables the synthesis of a diverse range of N-sulfonyl amines,and subsequent diversification of the addition products showcases the synthetic potential of this protocol.

Accelerating Deprotonation Kinetics of RuO_(2)for Efficient Acidic Water Oxidation

The development of a highly efficient noniridium-based oxygen evolution reaction catalyst is the key to realizing large-scale commercial application of the proton-exchange membrane water electrolyzer.RuO_(2)is the most promising alternative to IrO_(2),but if usually suffers from lattice-oxygenmediated corrosion and sluggish proton transfer kinetics under acidic media.Herein,we propose an effective strategy of embedding RuO_(2)nanoparticles into a N-doped carbon support,termed as RuO_(2)-NC,to simultaneously prevent Ru dissolution and accelerate the bridging-oxygen-assisted deprotonation process.The obtained RuO_(2)-NC electrocatalyst presents high activity with an overpotential of 159 mV to reach 10 mA cm^(−2) and remarkable stability for over 240 h.Structural investigation and theoretical calculations reveal that the electron-rich NC substrate,as an electron donor,provides a buffered charge compensation to protect RuO_(2)from excessive oxidation and lattice oxygen loss by switching into a conventional adsorbate evolution mechanism(AEM).More importantly,the activated bridging oxygen(Obri)sites can facilitate the deprotonation of*OOH intermediates,leading to an optimized bridging-oxygen-assisted deprotonation AEM pathway.

Insights into the biosynthesis of septacidin L-heptosamine moiety unveils a VOC family sugar epimerase

L-Heptopyranoses are important components of bacterial polysaccharides and biological active secondary metabolites like septacidin(SEP),which represents a group of nucleoside antibiotics with antitumor,antifungal,and pain-relief activities.However,little is known about the formation mechanisms of those L-heptose moieties.In this study,we deciphered the biosynthetic pathway of the L,L-gluco-heptosamine moiety in SEPs by functional characterizing four genes and proposed that SepI initiates the process by oxidizing the 4’-hydroxyl of L-glycero-α-D-manno-heptose moiety of SEP-328(2)to a keto group.Subsequently,SepJ(C5 epimerase)and SepA(C3 epimerase)shape the 4’-keto-L-heptopyranose moiety by sequential epimerization reactions.At the last step,an aminotransferase SepG installs the 4’-amino group of the L,L-gluco-heptosamine moiety to generate SEP-327(3).An interesting phenomenon is that the SEP intermediates with 4’-keto-L-heptopyranose moieties exist as special bicyclic sugars with hemiacetal-hemiketal structures.Notably,L-pyranose is usually converted from D-pyranose by bifunctional C3/C5 epimerase.SepA is an unprecedented monofunctional L-pyranose C3 epimerase.Further in silico and experimental studies revealed that it represents an overlooked metal dependent-sugar epimerase family bearing vicinal oxygen chelate(VOC)architecture.

Electrokinetic transport of nanoparticles in functional group modified nanopores

Nanopore detection is a hot issue in current research.One of the challenges is how to slow down the transport velocity of nanoparticles in nanopores.In this paper,we propose a functional group modified nanopore.That means a polyelectrolyte brush layer is grafted on the surface of the nanopore to change the surface charge properties.The existing studies generally set the charge density of the brush layer to a fixed value.On the contrary,in this paper,we consider an essential property of the brush layer:the volume charge density is adjustable with pH.Thus,the charge property of the brush layer will change with the local H+concentration.Based on this,we established a mathematical model to study the transport of nanoparticles in polyelectrolyte brush layer modified nanopores.We found that pH can effectively adjust the charge density and even the polarity of the brush layer.A larger pH can reduce the transport velocity of nanoparticles and improve the blockade degree of ion current.The grafting density does not change the polarity of the brush charge.The larger the grafting density,the greater the charge density of the brush layer,and the blockade degree of ion current is also more obvious.The polyelectrolyte brush layer modified nanopores in this paper can effectively reduce the nanoparticle transport velocity and retain the essential ion current characteristics,such as ion current blockade and enhancement.

Coordination behavior of N-benzoylamino acids: Synthesis and structure of mixed-ligand complexes of palladium(Ⅱ) with N-benzoylamino acid dianion and diamine

Four new mixed-ligand complexes of pailadiumt(Ⅱ) with L1(N-benzoyl-α-amino acid dianion) and L2[ethyldiamine (en),2,2’-bipyridine (Bpy) and 1,10-phenanthroline (Phen)] were synthesized.Ail the complexes have been characterized by elemental analyses,molar conductance,infrared and 1H NMR spectra and therme-gravimetric analyses.Crystal structures of [Pd(Bpy)(Bzval-N,O)] and [Pd(en) (Bzphe-N,O)] H2O have been do termmed by X-ray diffraction analysis.The results indicate that in all the complexes hgand L1 coordinates to palladium (Ⅱ) through deprotonated amide nitrogen and carboxylic oxygen,and there are some intramolecular nonrovalent in teractions in the complexes.

The hydrogen sulfate recognition properties of azo-salicylaldehyde schiff base receptors

Azo-salicylaldehyde Schiff base-typed receptors containing an acidic H-bond donor moiety were syn-thesized and characterized. The UV-Vis data indicate that these receptors could act as selective col-orimetric sensors for basic anions and acidic species hydrogen sulfate by different color changes in a water-containing medium. The experiment of Brφnsted acid-base reaction by adding the sodium hy-droxide or perchloric acid revealed that the mechanism of recognition of anions might be deprotona-tion/protonation of the OH fragments by interacting with different anions and that the deprotona-tion/protonation process is fully reversible. The deprotonation/protonation of the receptors is respon-sible for the dramatic color change.

Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

Two rosamine-based pH probes 1a and 1b with pyronine-phenol skeleton were designed and synthesized by a simple one-step reaction, pH titration experiments showed that probes 1a and 1b exhibit near OFF-ON fluorescence responses around 550--750 nm towards the hydrogen ions. The pKa of the probe 1a is 8.29, while that of the probe lb increases to 12.1 because of the hydrogen bond inside it. Selective and competitive experiments indicated that both common ions and amino acids did not interfere their emission with hydrogen ions. Moreover, confocal fluorescent imaging showed that the probe la could be served as mitochondria biomarker in HeLa and Ges-1 cells.

Zwitterionic Hydroboranes Stabilized by β-Diimine Framework

Reaction of the N-heterocyclic borane [MeCCHC（CHe）（NAr）2]Btt （1, Ar=2,6-Me2C6H3） with B（C6F5）3 af- forded the zwitterionic hydroborane [MeCCHC（CHz）B（C6F5）3（NAr）2]BH, in which the β-methyl group can be deprotonated with LiN（SiMe3）2 to yield an anionic zwitterionic borenium.

On-Chip Fabrication of Carbon Nanoparticle–Chitosan Composite Membrane

The on-chip fabrication of a carbon nanoparticle-chitosan composite membrane （i.e. a sorbent membrane or a mixed matrix membrane） using laminar flow-based interfacial deprotonation technology was presented in this paper. In addition, the effects of carbon nanoparticles and reactant flow rates on membrane formation were investigated. Finally, the permeability and adsorption capacities of the membrane were discussed. During fabrication, an acidic chitosan solution and a basic buffer solution that contained carbon nanoparticles were introduced into a microchannel. At the flow interface, a freestanding composite membrane with embedded carbon nanoparticles was formed due to the deprotonation of the chitosan molecules. The membrane growth gradually stopped with time from upstream to downstream and the thickness of the membrane increased rapidly and then slowly along the reactant flow direction. The formation of the membrane was divided into two stages. The average growth rate in the first stage was significantly larger than the average growth rate in the second stage. Carbon nanoparticles in the basic solution acted as nucleating agents and made the membrane formation much easier. As the flow rate of the chitosan solution increased, the averaged membrane thickness and the membrane hydraulic permeability initially increased and then decreased. Because of the addition of carbon nanoparticles, the formed membrane had adsorption abilities. The carbon nanoparticle-chitosan composite membrane that was fabricated in this study could be employed for simultaneous adsorption and dialysis in microdevices in the future.

Tandem Reaction of Deprotonation-Oxidation-Wittig Reaction: Stereoselective Synthesis of (E)-α,β-Unsaturated Enoates

Phosphonium or arsonium salt with primary alcohol can undergo the tandem reaction of deprotonation-oxidation-Wittig reaction in the presence of sodium hydroxide and manganese dioxide, providing a general and efficient method for the stereoselective synthesis of (E) -α, β-unsaturated enoates.