CB[7]- and CB[8]-Based [2]-(Pseudo)rotaxanes with Triphenylphosphonium-Capped Threads: Serendipitous Discovery of a New High-Affinity Binding Motif

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] The synthesis of new triphenylphosphonium-capped cucurbit[7]uril (CB[7])- and cucurbit[8]uril (CB[8])-based [2]rotaxanes was achieved by a simultaneous threading-capping strategy. While the use of CB[7] produced the designed [2]rotaxane, attempts to obtain the CB[8] analogue were unsuccessful due to the unexpected strong interaction found between the host and the phosphonium caps leading to pseudo-heteroternary host–guest complexes. This unusual binding motif has been extensively studied experimentally, with results in good agreement with those obtained by dispersion-corrected DFT methods.This research was supported by the Agencia Estatal de Investigación (PID2019-105272GB-I00) and Xunta de Galicia (ED431C 2018/39). I.N. thanks the MECD (FPU program). The authors are indebted to Centro de Supercomputación de Galicia (CESGA) for providing the computer facilitiesXunta de Galicia; ED431C 2018/3

Reversible Control of DNA Binding with Cucurbit[8]uril-Induced Supramolecular 4,4′-Bipyridinium–Peptide Dimers

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUGThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.bioconjchem.1c00063[Abstract] Many cellular processes in living organisms are regulated by complex regulatory networks, built from noncovalent interactions between relatively few proteins that perform their functions by switching between homo- and heterooligomeric assemblies or mono- and bivalent states. Herein, we demonstrate that the conjugation of a 4,4′-bipyridinium scaffold to the basic region of the GCN₄ bZip transcription factor can be exploited to control the dimerization of the conjugate by formation of a supramolecular complex with cucurbit[8]uril. Importantly, this supramolecular complex is able to specifically recognize its target dsDNA, and this binding can be reversibly switched by the application of external stimuli.We are thankful for the funding received from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 851179), the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (FEDER) (CTQ2016-75629-P), the Agencia Estatal de Investigación and FEDER (CTQ2017-89166-R and PID2019-105272GB-I00) and the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39). P.N thanks the Ministerio de Ciencia, Innovación y Universidades for her PhD fellowship (FPU17/04357). E.P. thanks the UDC-Inditex InTalent Programme for her research contract and funding and the Xunta de Galicia for the Oportunius ProgrammeXunta de Galicia; ED431C 2018/39https://pubs.acs.org/doi/suppl/10.1021/acs.bioconjchem.1c00063/suppl_file/bc1c00063_si_001.pd

Self-Assembled Peptide–Inorganic Nanoparticle Superstructures: From Component Design to Applications

[Abstract] Peptides have become excellent platforms for the design of peptide–nanoparticle hybrid superstructures, owing to their self-assembly and binding/recognition capabilities. Morover, peptide sequences can be encoded and modified to finely tune the structure of the hybrid systems and pursue functionalities that hold promise in an array of high-end applications. This feature article summarizes the different methodologies that have been developed to obtain self-assembled peptide–inorganic nanoparticle hybrid architectures, and discusses how the proper encoding of the peptide sequences can be used for tailoring the architecture and/or functionality of the final systems. We also describe the applications of these hybrid superstructures in different fields, with a brief look at future possibilities towards the development of new functional hybrid materials.We are thankful for the funding received from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 851179), the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (FEDER) (CTQ2016-75629-P), the Agencia Estatal de Investigación and FEDER (CTQ2017-89166-R) and the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39). E. P. thanks the UDC-Inditex InTalent Programme for her research contract and funding and the Xunta de Galicia for the Oportunius ProgrammeXunta de Galicia; ED431C 2018/3

Phase space contraction and quantum operations

We give a criterion to differentiate between dissipative and diffusive quantum operations. It is based on the classical idea that dissipative processes contract volumes in phase space. We define a quantity that can be regarded as ``quantum phase space contraction rate'' and which is related to a fundamental property of quantum channels: non-unitality. We relate it to other properties of the channel and also show a simple example of dissipative noise composed with a chaotic map. The emergence of attaractor-like structures is displayed.Comment: 8 pages, 6 figures. Changes added according to refferee sugestions. (To appear in PRA

Amino Acid–Viologen Hybrids: Synthesis, Cucurbituril Host–Guest Chemistry, and Implementation on the Production of Peptides

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] We present herein the development of a series of viologen–amino acid hybrids, obtained in good yields either by successive alkylations of 4,4′-bipyridine, or by Zincke reactions followed by a second alkylation step. The potential of the obtained amino acids has been exemplified, either as typical guests of the curcubituril family of hosts (particularly CB[7]/[8]) or as suitable building blocks for the solution/solid-phase synthesis of two model tripeptides with the viologen core inserted within their sequences.The authors are grateful for the funding received from the Agencia Estatal de Investigación and FEDER (PID2019-105272GB-I00 and CTQ2017-89166-R), the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39 and 508/2020), and the European Research Council (Grant Agreement No. 851179). I.N. thanks the MECD (FPU program) for financial support. E.P. thanks the Agencia Estatal de Investigación for her Ramón y Cajal contract (RYC2019-027199-I). Funding for open access charge: Universidade da Coruña/CISUGXunta de Galicia; ED431C 2018/39Xunta de Galicia; ED431C 508/202

Solid-Phase Zincke Reaction for the Synthesis of Peptide-4,4′-bipyridinium Conjugates

Author accepted manuscript[Abstract] We present herein the development of a new synthetic strategy for the conjugation of 4,4′-bipyridinium derivatives into peptide scaffolds. The methodology, based on the development of a solid-phase version of the Zincke reaction between activated pyridinium salts and amines, is able to produce the desired conjugates in a straightforward fashion, with the bipyridinium units attached at the N-terminus of peptides or at Lys side chains of N-terminal acetylated peptides.This work has received financial support from the Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional (FEDER) (CTQ2016-75629-P), Agencia Estatal de Investigación and FEDER (CTQ2017-89166-R), and the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39)Xunta de Galicia; ED431C 2018/3

Observation of the Bloch-Siegert Shift in a Qubit-Oscillator System in the Ultrastrong Coupling Regime

We measure the dispersive energy-level shift of an $LC$ resonator magnetically coupled to a superconducting qubit, which clearly shows that our system operates in the ultrastrong coupling regime. The large mutual kinetic inductance provides a coupling energy of $\approx0.82$~GHz, requiring the addition of counter-rotating-wave terms in the description of the Jaynes-Cummings model. We find a 50~MHz Bloch-Siegert shift when the qubit is in its symmetry point, fully consistent with our analytical model.Comment: Published version (4 pages, 4 figures), including supplementary material (2 pages, 4 figures

Vermellogens and the Development of CB[8]-Based Supramolecular Switches Using pH-Responsive and Non-Toxic Viologen Analogues

[Abstract] We present herein the “vermellogens”, a new class of pH-responsive viologen analogues, which replace the direct linking between para-substituted pyridinium moieties within those by a hydrazone functional group. A series of such compounds have been efficiently synthesized in aqueous media by hydrazone exchange reactions, displaying a marked pH-responsivity. Furthermore, the parent N,N′-dimethylated “vermellogen”: the “red thread”, an analogue of the herbicide paraquat and used herein as a representative model of the series, showed anion-recognition abilities, non-reversible electrochemical behavior, and non-toxicity of the modified bis-pyridinium core. The host–guest chemistry for the “red thread” with the CB[7,8] macrocyclic receptors has been extensively studied experimentally and by dispersion corrected density functional theory methods, showing a parallel behavior to that previously described for the herbicide but, crucially, swapping the well-known redox reactive capabilities of the viologen-based inclusion complexes by acid–base supramolecular responsiveness.This work is supported by Grants PID2019-105272GB-I00 and CTQ2017-89166-R funded by MCIN/AEI/10.13039/501100011033 and the Consellería de Educación, Universidade e Formación Profesional, Xunta de Galicia (ED431C 2018/39 and 508/2020). A.B.-G., I.N., and R.S. thank, respectively, Xunta de Galicia (ED481B-2021-099), the MECD (FPU program), and Erasmus+ program for financial support. We are very grateful for helpful discussions with Professors Hao Li (Zhejiang University), Patrice Woisel (Université de Lille) and José Luis Barriada (Universidade da Coruña). We also acknowledge the use of RIAIDT-USC analytical facilities, and CESGA (Xunta de Galicia) for computational time.Xunta de Galicia; ED431C 2018/39Xunta de Galicia; ED431C 508/2020Xunta de Galicia; ED481B-2021-09

Thinking Outside the Blue Box: Induced Fit within a Unique Self-Assembled Polycationic Cyclophane

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society.[Abstract] We present herein the development of a new polycationic molecular receptor, inspired by the ubiquitous cyclobis(paraquat-p-phenylene)cyclophane (“blue box”). Our analogue, the “white box”, has been easily self-assembled on a preparative scale in water, using a template-assisted process by acyl hydrazone bonding of complementary bis(pyridinium)xylylene tweezers, followed by kinetic trapping of the empty receptor. The obtained macrocycle was found to display a marked pH responsiveness in water, because of an abnormal acidity of the amide protons within its structure. Consequently, and because of the concurrence of rotational isomerism under acidic conditions (fixed at higher pH values), the compound was found to display a dual behavior as a conformationally locked/flexible molecular host, being able to recognize appropriate aromatic substrates, in a lock and key or induced fit fashion, by a conjunction of π–π, C–H···π, and, crucially, the hydrophobic effect.This research was supported by the Ministerio de Economía y Competitividad (MINECO FEDER, Grant CTQ2016-75629-P