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Intracellular accumulation of mutant proteins causes proteinopathies, which lack targeted therapies. Autosomal dominant hearing loss (DFNA67) is caused by frameshift mutations in OSBPL2. Here, we show that DFNA67 is a toxic proteinopathy. Mutant OSBPL2 accumulated intracellularly and bound to macroautophagy/autophagy proteins. Consequently, its accumulation led to defective endolysosomal homeostasis and impaired autophagy. Transgenic mice expressing mutant OSBPL2 exhibited hearing loss, but osbpl2 knockout mice or transgenic mice expressing wild-type OSBPL2 did not. Rapamycin decreased the accumulation of mutant OSBPL2 and partially rescued hearing loss in mice. Rapamycin also partially improved hearing loss and tinnitus in individuals with DFNA67. Our findings indicate that dysfunctional autophagy is caused by mutant proteins in DFNA67; hence, we recommend rapamycin for DFNA67 treatment. Abbreviations: ABR: auditory brainstem response; ACTB: actin beta; CTSD: cathepsin D; dB: decibel; DFNA67: deafness non-syndromic autosomal dominant 67; DPOAE: distortion product otoacoustic emission; fs: frameshift; GFP: green fluorescent protein; HsQ53R-TG: human p.Q53Rfs*100-transgenic: HEK 293: human embryonic kidney 293; HFD: high-fat diet; KO: knockout; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NSHL: non-syndromic hearing loss; OHC: outer hair cells; OSBPL2: oxysterol binding protein-like 2; SEM: scanning electron microscopy; SGN: spiral ganglion neuron; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TG: transgenic; WES: whole-exome sequencing; YUHL: Yonsei University Hearing Loss; WT: wild-type.

This phenotype-genotype study aimed to investigate the extent of audioprofile variability related to cochlin major domains and to identify potential ethnic-specific differences associated with COCH-related hearing loss. Eight Korean families (26 cases) were diagnosed with COCH-related hearing loss by exome sequencing. Audiometric test results were combined with those from nine published East Asian families (20 cases) and compared with those from 38 European-descent families (277 cases). Audioprofiles were created by grouping audiometric test results into age ranges by age at testing and then averaging hearing loss thresholds by frequency within age ranges. The functional impact of the identified variants was assessed in vitro by examining the intracellular trafficking, secretion, and cleavage of cochlin. In both East Asian and European-descent families segregating COCH-related hearing loss, deafness-associated variants in non-LCCL domains of cochlin were associated with hearing loss that was more severe earlier in life than hearing loss caused by variants in the LCCL domain. Consistent with this phenotypic difference, functional studies demonstrated distinct pathogenic mechanisms for COCH variants in a domain-dependent manner; specifically, a cytotoxic effect was observed for the p.Phe230Leu variant, which is located in the vWFA1 domain. No ethnic-specific differences in hearing loss progression were observed, except for those attributable to an overrepresentation of presymptomatic cases in the European-descent cohort.

Ski-slope hearing loss (HL), which refers to increased auditory threshold at high frequencies, is common in adults. However, genetic contributions to this post-lingual HL remain largely unknown. Here, we prospectively investigated deafness-associated and novel candidate genes causing ski-slope HL. We analyzed 192 families with post-lingual HL via gene panel and/or exome sequencing. With an overall molecular diagnostic rate of 35.4% (68/192) in post-lingual HL, ski-slope HL showed a lower diagnostic rate (30.7%) compared with other conditions (40.7%). In patients who showed HL onset before the age of 40, genetic diagnostic probability was significantly lower for ski-slope HL than for other conditions. Further analysis of 51 genetically undiagnosed patients in the ski-slope HL group identified three variants in delta-like ligand 1 (DLL1), a Notch ligand, which presented in vitro gain-of-function effects on Notch downstream signaling. In conclusion, genetic diagnostic rates in post-lingual HL varied according to audiogram patterns with age-of-onset as a confounding factor. DLL1 was identified as a candidate gene causing ski-slope HL.

Development of SAR in a 5-aryl-3-acylpyridinyl-pyrazoles and 1-aryl-4-acylpyridinyl imidazoles series of mGlu5 receptor negative allosteric modulators (mGluR5 NAMs) using a functional cell-based assay is described in this Letter. Analysis of the Ligand-lipophilic efficiency (LipE) of compounds provided new insight for the design of potent mGluR5 negative allosteric modulators with anti-depressant activities.

A higher performance DRAM is required by the market due to the increasing of bandwidth of networks and the rise of high-capacity multimedia content. DDR4 SDRAM is the next-generation memory that meets these demands in computing and server systems. In comparison with current DDR3 memory, the major changes are supply voltage reduction to 1.2V, pseudo open drain I/O interface, and data rate increase from 1.6 to 3.2Gb/s. To achieve high performance at low supply voltage and reduce power consumption, this work introduces new functions and describes their implementation. Data bus inversion (DBI) is employed for high-speed transactions to reduce power consumption of I/O and SSN noise. Dual-error detection, which adopts cyclic redundancy check (CRC) for DQ, and command address (CA) parity is designed to guarantee reliable transmission. GDDR5 memory also has DBI and CRC functions [1], but in this work, these schemes are implemented in a way that reduces area overhead and timing penalty. Besides these error-check functions, an enhanced gain buffer and a PVT-tolerant fetch scheme improve basic receiving ability. To meet the output jitter requirements of DDR4 SDRAM, the type of delay line for DLL is selected at initial stage according to data rate.

The cyclic fatigue behavior of short fiber reinforced metal matrix composites was studied. Three fatigue life prediction models were developed by monitoring the resultant maximum strain and counts of acoustic emission during cyclic fatigue. Their increasing trends with the number of fatigue cycles were studied using the assumption that they can be expressed as a power-law function of the fatigue cycle number. Post-fatigue static tension tests were conducted to examine the degradation of the damaged materials. The acoustic emission count accumulated during tension testing decreased as the applied fatigue cycles increased; this change was also used to formulate life prediction models. All the new models show a better agreement to experimental data than do the existing equations.

A new test method including the tool shape and test procedure was developed to evaluate sheet metal formability using the finite element method (FEM). This method is intended to generate the various modes of deformation and to control the onset of failure independently under each mode so that the forming limit diagram (FLD) achieves a good representation of a wide range of strains. A blank holder force–punch stroke diagram with three failure loci is introduced to define the optimum process condition and the formability index by which each material is quantitatively evaluated. The test procedure of this method consists of three steps: drawing a blank holder force (BHF)–punch stroke diagram, measuring strains from the part stamped at the optimum process condition, and grading the test materials using the formability index. In numerical simulations under optimum process conditions, sheet metals can fail due to multi-mode rupture; this failure leads to a widely balanced strain distribution in the FLD such that strains are developed near the forming limit over a wide range of forming modes. Experiments were conducted on three grades of steel sheets to validate the proposed method. Stamping results yield well-defined strain signatures having a wide range of strain distribution in the FLD in all materials tested. The outcomes of the shape and strain behaviors agree well with the numerical results.

Conductive polymer composites (CPCs) consisting of expanded graphite (EG), flake-type graphite (FG) and thermalsetting resin were fabricated by means of a preform molding technique. Conductive fillers, EG and FG, were mechanically mixed with the phenol resin to provide an electrical property to composites. The filler loadings were fixed at 75wt.% to obtain a high electrical conductivity. The mechanical and electrical properties of CPCs were optimized according to the weight ratio and the particle size of FG. As the weight ratio increased, the flexural strength increased, however, the electrical conductivity decreased for both cases of CPCs using different sizes of FG. The particle size was an important parameter to change the mechanical and electrical behaviors. The flexural strength was sensitive to the particle size due to the different level of densification. The electrical conductivity also showed size-dependent behavior because of the different contribution to the conductive networking.

A preform moulding technique using expanded graphite is developed to manufacture composite bipolar plates for proton exchange membrane fuel cells (PEMFCs). The preform is composed of expanded graphite, graphite flake and phenol resin. Preforms utilizing the tangled structure of expanded graphite are easily fabricated at a low pressure of 0.07–0.28 MPa. A pre-curing temperature (100 °C) slightly above the melting point of phenol powders (90 °C) induces moderate curing, but also prevents excessive curing. After the preform is placed in a steel mould, compression moulding is carried out at high pressure (10 MPa) and temperature (150 °C). The fabrication conditions are optimized by checking the electrical conductivity, flexural strength and microstructure of the composite. The optimized electrical conductivity and flexural strength, 250 S cm−1 and 50 MPa, respectively, met the requirements for PEMFC bipolar plates.

Polymer electrolyte membranes consisting of AgBF 4 dissolved in poly(ethylene phthalate) (PEP) exhibit significantly better long-term stability of performance in the separation of propylene/propane mixtures than AgBF 4 in poly(2-ethyl-2-oxazoline) (POZ) membranes. This improvement in stability is due to the suppression of the reduction of silver ions to silver metal nanoparticles by the formation of stable chelates between the phthalic groups of PEP and silver ions, which was confirmed by the observation of a large shift of the PEP CO stretching band with the addition of AgBF 4 ; the peak shift for PEP/AgBF 4 is twice that for POZ/AgBF 4 . Transmission electron micrograph (TEM) results confirmed that the rate of silver metal nanoparticle formation in PEP/AgBF 4 is significantly lower than that in POZ/AgBF 4 . We conclude that the strong coordination between phthalic groups in PEP and silver ions which results in the formation of stable chelates is of pivotal importance in preventing the reduction of silver ions to silver metal and consequently in improving the performance of the membrane in the separation of propylene/propane mixtures.

During the past decade, there has been much debate about the enormous catalytic rate enhancement observed in enzymatic reactions involving carbanion intermediates. Our recent theoretical study has demonstrated the importance of the short strong hydrogen bond (SSHB) in the enzymatic reactions. Nevertheless, other recent theoretical studies espouse the role of preorganization over that of the SSHB. To achieve a consensus on this issue and to find the truth, a more clarified explanation must be given. To this end, we have carried out an elaborate analysis of these enzymatic reactions. We here clarify that the catalytic mechanism needs to be explained with three important factors, viz., SSHB, preorganization, and charge buffering/dissipation. Since the charge buffering role is different from the commonly used concepts of the SSHB and preorganization (unless these definitions are expanded), we stress that the charge buffering role of the catalytic residues is an important ingredient of the enzymatic reaction in reducing the level of accumulation of the negative charge on the substrate during the reaction process. This charge reduction is critical to the lowering of activation barriers and the stabilization of intermediates.

We measured and analyzed the subthreshold degradation of the gate-all-around (GAA) silicon nanowire field-effect transistors with the length of 300/500 nm and the radius of 5 nm. An analytical model incorporating the effect of interface traps quantitatively explained the measured subthreshold swing (SS) degradation. A simple electrostatic argument showed that the GAA device had smaller degradation of SS values than planar devices for the same interface trap densities.

Relative stabilities of cucurbit[n]uril homologues (CB[n]; n = 4−7) and decamethylcucurbit[n]uril homologues (DCB[n]; n = 4−6) have been inspected with ab initio and density functional theory (DFT) calculations. Results show that CB[6] and CB[7] are more stable among CB[n] homologues and DCB[5] among DCB[n] homologues, which confirms the previous experiments. This is also supported in consideration of the puckering angles of the respective dimeric building units. Our investigation on the template effect in the formation of CB and DCB macrocyclic structure suggests that H3O+ is important in tethering the building units being added to the macrocyclic structure in the course of the reaction. The presence of acid tends to favor the structures of smaller-size homologues. Thus, in consideration of the acid contents in the experiments, our calculations explain why CB[6] and DCB[5] are the major products. Moreover, it explains why considerable amount of CB[7] could be obtained in the recent report in which the am...

On the basis of the active site topology and enzymic catalytic mechanism of carboxypeptidase A (CPA), a prototypical zinc-containing proteolytic enzyme, alpha-benzyl-2-oxo-1,3-oxazolidine-4-acetic acid (1), was designed as a novel type of mechanism-based inactivator of the enzyme. All four possible stereoisomers of the inhibitor were synthesized in an enantiomerically pure form starting with optically active aspartic acid, and their CPA inhibitory activities were evaluated to find that surprisingly all of the four stereoisomers inhibit CPA in a time dependent manner. The inhibited enzyme did not regain its enzymic activity upon dialysis. The inactivations were prevented by 2-benzylsuccinic acid, a competitive inhibitor that is known to bind the active site of the enzyme. These kinetic results strongly support that the inactivators attach covalently to the enzyme at the active site. The analysis of ESI mass spectral data of the inactivated CPA ascertained the conclusion from the kinetic results. The values of second-order inhibitory rate constants (k(obs)/[I](o)) fall in the range of 1.7-3.6 M(-1) min(-1). The lack of stereospecificity shown in the inactivation led us to propose that the ring cleavage occurs by the nucleophilic attack at the 2-position rather than at the 5-position and the ring opening takes place in an addition-elimination mechanism. The tetrahedral transition state that would be generated in this pathway is thought to be stabilized by the active site zinc ion, which was supported by the PM3 semiemprical calculations. In addition, alpha-benzyl-2-oxo-1,3-oxazolidine-5-acetic acid (18), a structural isomer of 1 was also found to inactivate CPA in an irreversible manner, reinforcing the nucleophilic addition-elimination mechanism. The present study demonstrates that the transition state for the inactivation pathway plays a critical role in determining stereochemistry of the inactivation.

[formula: see text] A novel type of palladium-catalyzed cascade cyclization-coupling reaction that proceeds with suppressed beta-hydride elimination has been found. One of the N-sulfonyl oxygens is suggested to coordinatively stabilize an alkylpalladium intermediate, thus preventing the intermediate from the usual beta-elimination. This is the first sequential palladium-catalyzed coupling reaction where the Suzuki and Heck reactions can compete. The reaction provides an efficient synthetic route to 4-methylene-3-arylmethylpyrrolidines, which are not readily available by other routes.

The mobility-degradation factor and the series resistance of cylindrical gate-all-around silicon nanowire field-effect transistors are extracted using the same mobility-degradation model as in the case of planar MOSFETs. The extraction is done by defining an asymptotic voltage as a function of the saturation current measured from devices with various lengths. The extracted mobility-degradation factor is an order of magnitude larger than those of other planar MOSFETs. This result suggests that, while the all-around gate can turn off the electron channel effectively, it creates more interface scattering in the strong inversion condition. The extracted series resistance is mostly due to the crowding of the electron flow along the sidewall of the n+ contact region making an abrupt joint with the nanowire.

Delta(5)-3-Ketosteroid isomerase from Pseudomonas testosteroni has been intensively studied as a prototype to understand an enzyme-catalyzed allylic isomerization. Asp(38) (pK(a) approximately 4.7) was identified as the general base abstracting the steroid C4beta proton (pK(a) approximately 12.7) to form a dienolate intermediate. A key and common enigmatic issue involved in the proton abstraction is the question of how the energy required for the unfavorable proton transfer can be provided at the active site of the enzyme and/or how the thermodynamic barrier can be drastically reduced. Answering this question has been hindered by the existence of two differently proposed enzyme reaction mechanisms. The 2.26 A crystal structure of the enzyme in complex with a reaction intermediate analogue equilenin reveals clearly that both the Tyr(14) OH and Asp(99) COOH provide direct hydrogen bonds to the oxyanion of equilenin. The result negates the catalytic dyad mechanism in which Asp(99) donates the hydrogen bond to Tyr(14), which in turn is hydrogen bonded to the steroid. A theoretical calculation also favors the doubly hydrogen-bonded system over the dyad system. Proton nuclear magnetic resonance analyses of several mutant enzymes indicate that the Tyr(14) OH forms a low barrier hydrogen bond with the dienolic oxyanion of the intermediate.

A nonmonotonic, decay−growth−decay type forced Rayleigh scattering (FRS) decay profile was observed in the study of methyl red (o-MR) diffusion in polymer solutions in which the carboxylic hydrogen of o-MR can form a hydrogen bond with polymer chain segments (Lee and Lodge, J. Phys. Chem. 1987, 91, 5546; Lee et al. Macromolecules 1992, 25, 6977). The diffusivities of ground state o-MR (trans form) and of its photoexcited isomer (cis form) are different enough to show the nonmonotoic decay profile, but the origin of the behavior has not been fully understood. In order to elucidate this observation, the dependence of the decay profile shape on polymer concentration as well as on tempreature was investigated by FRS. From the results, we propose that the internal hydrogen-bonding strength between the carboxylic hydrogen and the azo nitrogen in o-MR changes upon photoisomerization from the trans to cis form, which results in the different diffusivities of the two isomers in hydrogen-bonding media. This proposi...

The first comprehensive ab initio study is performed on an excess electron bound to the water dodecamer to find out if this wet electron can be regarded as a precursor of the fully solvated electron. Various structures of the wet electron are explored using ab initio calculations. Among a number of possible geometries categorized as unbounded, surface, internal, and partially internal excess-electron states, the lowest-energy conformer is predicted to be a structure of a partially internal state. The predicted vertical electron-detachment energy of this structure is in good agreement with the experimental value of Coe et al. [J. Chem. Phys. 92, 3980 (1990)]. This indicates that in the experiment the partially internal excess-electron state structure would have been detected. The electronic structure, interactions between the excess electron and dangling H atoms (e⋯ H interaction), and red-shifts of the O–H stretching frequencies with strong IR intensities are discussed.

Understanding the origin of the regioselectivity of inositol derivatives is essential to the synthetic design of these biologically important molecules. We have undertaken a study of the regioselectivities displayed by the myo-inositol derivatives toward electrophiles using various levels of quantum mechanical calculation: Hartree−Fock (HF) theory, Moller-Plesset second-order perturbation (MP2) theory, density functional theory (DFT), and self-consistent reaction field (SCRF) theory. Various basis sets were also tested. The systems investigated here are 1,2:4,5-di-O-methylidene-myo-inositol and its probable intermediates (deprotonated and sodium-chelated species). In experiments the O3 position was the major site for derivatization of the molecule. However, the MP2 and DFT results could not explain the experiments. Taking into account that the myo-inositol derivatives were highly insoluble with the exception of some polar solvents, we performed the SCRF calculations using the dielectric constant (e) of 4...

Inositol phosphate derivatives play key roles in intracellular signal transduction. The X-ray structure of 1,2:4,5-diisopropylidene-myo-inositol is different from the conformer predicted by NMR and IR spectra. Therefore, we performed ab initio conformational study of the molecule, as a preliminary study before investigating the regioselectivity displayed by the myo-inositol toward electrophiles. The relative stabilities of four possible conformers of the molecule were investigated at various levels of ab initio theory: Hartree−Fock (HF) theory, Moller−Plesset second-order perturbation (MP2) theory, density functional theory (DFT), and self-consistent reaction field (SCRF) theory. Various basis sets were also tested. All calculations gave a consistent result which shows strong intramolecular hydrogen bonding interaction in an isolated system such as gas phase or solution. This is in agreement with NMR experiment. The frequency splitting between two OH vibrational frequencies due to the difference in the s...

Novel resistive random access memory (RRAM) cell structure without an access transistor or diode is proposed and fabricated. The cell structure is comprised of both a phase change material (GeSbTe) and a bipolar resistive switching material (TiO 2 ). The electrical properties of the proposed cell are also evaluated in order to verify the possibility of operation without an access transistor or diode. And then the cell access mechanism is proposed in order to operate our RRAM cell without an unexpected current path. By using our proposed RRAM cell structure, we expect that high density memory with the simple 4F2 cross-point structured cell array can be easily fabricated by two photo lithography processes.

The effects of Al layer and plasma oxidation amount on TiO 2 based bipolar RRAM cell are investigated, respectively. In Ir/Al/TiO 2 /Ir structure, VRESET is slightly lowered and the current ratio is increased. In case of plasma oxidation effect, the device which experienced short-time plasma oxidation has low set/reset voltages and high current and resistance ratios. These results are commonly thought to be induced by more oxygen vacancies.

Intracranial or intrathecal administration of certain AAV vectors for CNS gene transfer is accompanied with systemic leakage into off-target organs such as the liver and spleen. Both preclinical and clinical studies have highlighted potential concerns related to high vector dose-related immunotoxicity and more recently, hepatic genotoxicity in mouse models. In order to address these potential safety issues and reduce the effective dose required to achieve efficient transgene expression in the CNS, we have rationally engineered next generation AAV vectors that show robust CNS spread and efficient transduction, while demonstrating minimal leakage into the systemic circulation. Direct CNS administration or intrathecal infusion of AAV9 results in highly efficient gene expression in neuronal and glial cellular populations in neonatal and adult mice in vivo. However, AAV9 vectors are also disseminated into the blood circulation accompanied by broad vector biodistribution and reporter gene expression in the heart, liver, spleen and kidney. CNS-to-liver and CNS-to-spleen ratios of vector genome copy numbers ranging from 0.3 to 1 were observed. A prototype, engineered AAV strain demonstrated similar potential for spread and high transduction efficiency in neonatal and adult mice. However, transgene expression was primarily restricted to neurons and virtually no leakage into systemic organs was observed regardless of CNS injection route. Preliminary studies in rhesus macaques also confirm the ability of the engineered AAV strain to spread and globally transduce the primate brain. Additional biodistribution data from rodent and primate models is forthcoming. These studies provide a roadmap for addressing clinical gene therapy challenges through continued vector development and confirm that natural AAV isolates are excellent platforms for building next generation vectors with robust transduction efficiency and improved safety profiles.

In this paper, we present a very fast new GPU-based algorithm for volume rendering using the ray plane casting technique. It consists of preprocessing and main processing. In preprocessing, we reduce the waste of memory and produce the texture data which can be efficiently traversed concurrently in main processing by converting the volume data into a 2D texture of square shape in the frame buffer. In main processing, the ray plane casting and resampling are implemented by fragment programming which makes the efficient use of GPUs high performance. Early termination and space leaping have been used as acceleration techniques during the calculation of color and opacity in the fragment program on GPU using stencil and depth tests on GPU. We shall show that our GPU-based algorithm is much faster than CPU-based by the efficient fragment programming techniques used for ray plane interpolation, re-sampling and acceleration techniques.

Overwhelming data is produced during semiconductor processing and it becomes more important to classify a large number of wafers into various types of failures for the root cause analysis of the yield excursion as quickly as possible. In this paper, feature vector based methods have been suggested for the classification of wafers and their application to the root cause analysis. Local bin profile has been calculated to generate a feature vector for a wafer. K-means clustering method has been used to cluster these vectors for the classification of wafers. ANOVA or Kruscal-Wallis test has been applied to one of the components of a feature vector for the yield analysis, depending on its normality. Our yield analysis examples have proven that these analysis methods are very effective and quick in pinpointing the root cause for the various types of failures, especially the equipment-originated ones, including those otherwise would be impossible with the conventional methods

[reaction: see text] We present an ab initio study of the acid-promoted hydrolysis reaction mechanism of N-formylaziridine in comparison with formamide. Since the rate of amide hydrolysis reactions depends on the formation of the tetrahedral intermediate, we focused our attention mainly on the reactant complex, the tetrahedral intermediate, and the transition state connecting these two stationary points. Geometries were optimized using the density functional theory, and the energetics were refined using ab initio theory including electron correlation. Solvent effects were investigated by using polarizable continuum method calculations. The proton-transfer reaction between the O-protonated and N-protonated amides was investigated. In acidic media, despite that the N-protonated species is more stable than the O-protonated one, it is predicted that both N-protonated and O-protonated pathways compete in the hydrolysis reaction of N-formylaziridine.

A benzene-based tripodal imidazolium receptor utilizing the strong (C-H)(+)...X(-) hydrogen bonding interaction between imidazolium moieties and halide anions is extensively investigated both theoretically and experimentally. Ab initio calculations predict that this receptor has a very high affinity for fluoride ion (F(-)). The association constant and free energy gain of the N-butyl receptor 2 for F(-) in acetonitrile were measured to be 2.1 x 10(5) M(-1) and -7.25 kcal/mol, respectively, showing that the receptor has a high affinity for F(-) in highly polar organic solvents.

[structure: see text] In consideration of competition between cation-pi and hydrogen bond interaction forces, we designed a novel receptor, 1,3,5-tris(pyrrolyl)benzene, which shows high selectivity for acetylcholine (ACh). The selectivity of the receptor for ACh over other ammonium cations is demonstrated by the ion-selective electrode (ISE) method in buffer solution. The binding free energy of the receptor with ACh in chloroform solution is measured to be 3.65 kcal/mol in the presence of chloride anion by nuclear magnetic resonance spectroscopy, and that in water is estimated to be much greater ( approximately 6 kcal/mol).

[structure: see text]Given the recent report of a novel pyrazole receptor exhibiting a high selectivity for NH4+ over K+, it would be interesting to investigate the origin of this selectivity and affinity so that better receptors could be designed. On the basis of extensive theoretical studies, we conclude that the origin arises from a subtle interplay of charged H-bonds and cation-pi interactions. The approach employed herein would be very useful in the rational design of novel functional molecular systems.

A two-step reaction mechanism (catalyzed alternatively by acid and base) with partial proton shuttles and charge redistributions promoted by short strong H bonds (SSHBs) (playing a dual role as an amphi-acid/base catalyst) is proposed to explain the enormous rate enhancement observed in enzymatic reactions involving carbanion intermediates. The SSHBs in the two-step reactions are found to be responsible for enhancing enzyme–substrate interactions in favor of the transition state structure over that of reactant. The detailed quantum theoretical studies of ketosteroid isomerase provide evidence of assisting roles of SSHB in enzymatic activity. The understanding of the two-step reaction mechanism would be a useful aid in designing novel functional enzymes and abzymes.

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