Proton Transfer
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2022 ◽  
Vol 12 (1) ◽  
Chiara Schiattarella ◽  
Carlo Diaferia ◽  
Enrico Gallo ◽  
Bartolomeo Della Ventura ◽  
Giancarlo Morelli ◽  

AbstractThe self-assembling of small peptides not only leads to the formation of intriguing nanoarchitectures, but also generates materials with unexpected functional properties. Oligopeptides can form amyloid-like cross-β assemblies that are able to emit intrinsic photoluminescence (PL), over the whole near-UV/visible range, whose origin is still largely debated. As proton transfer between the peptide chain termini within the assembly is one of the invoked interpretations of this phenomenon, we here evaluated the solid state PL properties of a series of self-assembled hexaphenylalanine peptides characterized by a different terminal charge state. Overall, our data indicate that the charge state of these peptides has a marginal role in the PL emission as all systems exhibit very similar multicolour PL associated with a violation of the Kasha’s rule. On the other hand, charged/uncharged ends occasionally produce differences in the quantum yields. The generality of these observations has been proven by extending these analyses to the Aβ16–21 peptide. Collectively, the present findings provide useful information for deciphering the code that links the spectroscopic properties of these assemblies to their structural/electronic features.

Shinya Kano ◽  
Harutaka MEKARU

Abstract We study a proton transport on the surface of insulating nanoparticles for humidity sensors. We use the approach to reveal proton transfer mechanisms in humidity sensitive materials. Hydrophilic and hydrophobic ligand-terminated silica nanoparticle films are adopted for evaluating temperature dependence of the ion conductivity. According to the activation energy of the conductivity, we explain the Grotthuss (H+ transfer) and vehicular (H3O+ transfer) mechanisms are mainly dominant on hydrophilic (-OH terminated) and hydrophobic (acrylate terminated) surface of nanoparticles, respectively. This investigation gives us a clue to understand a proton transfer mechanism in solution-processed humidity-sensitive materials such as oxide nanomaterials.

2022 ◽  
Zihan Ma ◽  
Xiang-Mei Shi ◽  
Shin-ichi Nishimura ◽  
Seongjae Ko ◽  
Masashi Okubo ◽  

Abstract Developing high-power battery chemistry is an urgent task to buffer fluctuating renewable energies and achieve a sustainable and flexible power supply. Owing to the small size of proton and its ultrahigh mobility in water via the Grotthuss mechanism, aqueous proton batteries are an attractive candidate for high-power energy storage devices. Although Grotthuss proton transfer usually occurs in hydrogen-bonded networks of water molecules, in this work, we discover anhydrous Grotthuss-type proton transport in a dense oxide-ion array of solid α-MoO3 even without structural water. The fast proton transfer and accumulation that occurs during (de)intercalation in α-MoO3 is unveiled using both experiments and first-principles calculations. Coupled with a zinc anode and a superconcentrated dual-ion Zn2+/H+ electrolyte, the solid-state anhydrous Grotthuss proton transport mechanism realizes an aqueous MoO3-Zn battery with both high energy and power densities.

Boris Ucur ◽  
Alan T. Maccarone ◽  
Shane R. Ellis ◽  
Stephen J. Blanksby ◽  
Adam J. Trevitt

Jiang Bian ◽  
Anthony Cruz ◽  
Gabriel Lopez-Morales ◽  
Anton Kyrylenko ◽  
Donna McGregor ◽  

Histidine (an imidazole-based amino acid) is a promising building block for short aromatic peptides containing a proton donor/acceptor moiety. Previous studies have shown that polyalanine helical peptides substituted at regular intervals with histidine residues exhibit both structural stability as well as high proton affinity and high conductivity. Here, we present first-principle calculations of non-aqueous histidine-containing 310-,  and -helices and show that they are able to form hydrogen-bonded networks mimicking proton wires that have the ability to shuttle protons via the Grotthuss shuttling mechanism. The formation of these wires enhances the stability of the helices, and our structural characterizations confirm that the secondary structures are conserved despite distortions of the backbones. In all cases, the helices exhibit high proton affinity and proton transfer barriers on the order of 1~4 kcal/mol. Zero-point energy calculations suggest that for these systems, ground state vibrational energy can provide enough energy to cross the proton transport energy barrier. Additionally, ab initio molecular dynamics results suggests that the protons are transported unidirectionally through the wire at a rate of approximately 2 Å every 20 fs. These results demonstrate that efficient deprotonation-controlled proton wires can be formed using non-aqueous histidine-containing helical peptides.

Molecules ◽  
2022 ◽  
Vol 27 (1) ◽  
pp. 307
Fan Wang ◽  
Xiaoyan Ji ◽  
Fei Ying ◽  
Jiatao Zhang ◽  
Chongyang Zhao ◽  

We characterized the stationary points along the nucleophilic substitution (SN2), oxidative insertion (OI), halogen abstraction (XA), and proton transfer (PT) product channels of M− + CH3X (M = Cu, Ag, Au; X = F, Cl, Br, I) reactions using the CCSD(T)/aug-cc-pVTZ level of theory. In general, the reaction energies follow the order of PT > XA > SN2 > OI. The OI channel that results in oxidative insertion complex [CH3–M–X]− is most exothermic, and can be formed through a front-side attack of M on the C-X bond via a high transition state OxTS or through a SN2-mediated halogen rearrangement path via a much lower transition state invTS. The order of OxTS > invTS is inverted when changing M− to Pd, a d10 metal, because the symmetry of their HOMO orbital is different. The back-side attack SN2 pathway proceeds via typical Walden-inversion transition state that connects to pre- and post-reaction complexes. For X = Cl/Br/I, the invSN2-TS’s are, in general, submerged. The shape of this M− + CH3X SN2 PES is flatter as compared to that of a main-group base like F− + CH3X, whose PES has a double-well shape. When X = Br/I, a linear halogen-bonded complex [CH3−X∙··M]− can be formed as an intermediate upon the front-side attachment of M on the halogen atom X, and it either dissociates to CH3 + MX− through halogen abstraction or bends the C-X-M angle to continue the back-side SN2 path. Natural bond orbital analysis shows a polar covalent M−X bond is formed within oxidative insertion complex [CH3–M–X]−, whereas a noncovalent M–X halogen-bond interaction exists for the [CH3–X∙··M]− complex. This work explores competing channels of the M− + CH3X reaction in the gas phase and the potential energy surface is useful in understanding the dynamic behavior of the title and analogous reactions.

2022 ◽  
Vol 11 ◽  
Juan Li ◽  
Liangjie Lin ◽  
Xuemei Gao ◽  
Shenglei Li ◽  
Jingliang Cheng

ObjectivesTo analyze the value of amide proton transfer (APT) weighted and intravoxel incoherent motion (IVIM) imaging in evaluation of prognostic factors for rectal adenocarcinoma, compared with diffusion weighted imaging (DWI).Materials and MethodsPreoperative pelvic MRI data of 110 patients with surgical pathologically confirmed diagnosis of rectal adenocarcinoma were retrospectively evaluated. All patients underwent high-resolution T2-weighted imaging (T2WI), APT, IVIM, and DWI. Parameters including APT signal intensity (APT SI), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADC) were measured in different histopathologic types, grades, stages, and structure invasion statuses. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic efficacy, and the corresponding area under the curves (AUCs) were calculated.ResultsAPT SI, D and ADC values of rectal mucinous adenocarcinoma (MC) were significantly higher than those of rectal common adenocarcinoma (AC) ([3.192 ± 0.661%] vs. [2.333 ± 0.471%], [1.153 ± 0.238×10-3 mm2/s] vs. [0.792 ± 0.173×10-3 mm2/s], and [1.535 ± 0.203×10-3 mm2/s] vs. [0.986 ± 0.124×10-3 mm2/s], respectively; all P<0.001). In AC group, the APT SI and D values showed significant differences between low- and high-grade tumors ([2.226 ± 0.347%] vs. [2.668 ± 0.638%], and [0.842 ± 0.148×10-3 mm2/s] vs. [0.777 ± 0.178×10-3 mm2/s], respectively, both P<0.05). The D value had significant difference between positive and negative extramural vascular invasion (EMVI) tumors ([0.771 ± 0.175×10-3 mm2/s] vs. [0.858 ± 0.151×10-3 mm2/s], P<0.05). No significant difference of APT SI, D, D*, f or ADC was observed in different T stages, N stages, perineural and lymphovascular invasions (all P>0.05). The ROC curves showed that the AUCs of APT SI, D and ADC values for distinguishing MC from AC were 0.921, 0.893 and 0.995, respectively. The AUCs of APT SI and D values in distinguishing low- from high-grade AC were 0.737 and 0.663, respectively. The AUC of the D value for evaluating EMVI involvement was 0.646.ConclusionAPT and IVIM were helpful to assess the prognostic factors related to rectal adenocarcinoma, including histopathological type, tumor grade and the EMVI status.

2022 ◽  
Reman Kumar Singh ◽  
Rakesh Pant ◽  
G Naresh Patwari

The ability of phenol to transfer the proton to surrounding ammonia molecules in a phenol-(ammonia)n cluster will depend on the relative orientation of the ammonia molecules and a critical field of about 285 MV cm-1 is essential along the O–H bond for the transfer process. Ab-initio MD simulations reveal that for a spontaneous proton transfer process, the phenol molecule must be embedded in a cluster consisting of at least eight ammonia molecules, even though several local minima with proton transferred can be observed for clusters consisting of 5-7 ammonia molecules. Further, phenol solvated in large clusters of ammonia, the proton transfer is spontaneous with the proton transfer event being instantaneous (about 20-120 fs). These simulations indicate that the rate-determining step for the proton transfer process is the reorganization of the solvent around the OH group and the proton transfer process in phenol-(ammonia)n clusters. The fluctuations in the solvent occur until a particular set of configurations projects the field in excess of critical electric field along the O–H bond which drives the proton transfer process with a respone time of about 70 fs. Further, the proton transfer process follows a curvilinear path which includes the O–H bond elongation and out-of-plane movement of the proton and can be referred to as a “Bend-to-Break” process.

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