Cis Conformation Research Articles

Electric field modulation of electronic structure, charge transfer, and nonlinear optical properties of crocetin for dye-sensitized solar cells

Natural sensitizing dyes in solar energy applications have gained attention due to their sustainability, cost-effectiveness, and environmental friendliness. However, enhancing their performance, light-harvesting efficiency, and durability requires a deeper understanding of their structural and electronic properties under solar irradiance. Accordingly, this study explores the electronic structure and nonlinear optical properties of crocetin dye (cis and trans conformers) under varying external electric fields using M06-2X/6-311+G(d,p) model chemistry. The absorption characteristics strongly depend on field intensity, with electron injection efficiency expected to decrease as the field increases. Key nonlinear optical (NLO) parameters, such as dipole moment, polarizability, and hyperpolarizabilities, were calculated at solar irradiance peak frequencies. The NLO properties are wavelength-independent in the infrared region but show significant wavelength dependency in the visible region, increasing substantially near the absorption energy.

Sequence and structural determinants of RNAPII CTD phase-separation and phosphorylation by CDK7

The intrinsically disordered carboxy-terminal domain (CTD) of the largest subunit of RNA Polymerase II (RNAPII) consists of multiple tandem repeats of the consensus heptapeptide Y1-S2-P3-T4-S5-P6-S7. The CTD promotes liquid-liquid phase-separation (LLPS) of RNAPII in vivo. However, understanding the role of the conserved heptad residues in LLPS is hampered by the lack of direct biochemical characterization of the CTD. Here, we generated a systematic array of CTD variants to unravel the sequence-encoded molecular grammar underlying the LLPS of the human CTD. Using in vitro experiments and molecular dynamics simulations, we report that the aromaticity of tyrosine and cis-trans isomerization of prolines govern CTD phase-separation. The cis conformation of prolines and β-turns in the SPXX motif contribute to a more compact CTD ensemble, enhancing interactions among CTD residues. We further demonstrate that prolines and tyrosine in the CTD consensus sequence are required for phosphorylation by Cyclin-dependent kinase 7 (CDK7). Under phase-separation conditions, CDK7 associates with the surface of the CTD droplets, drastically accelerating phosphorylation and promoting the release of hyperphosphorylated CTD from the droplets. Our results highlight the importance of conformationally restricted local structures within spacer regions, separating uniformly spaced tyrosine stickers of the CTD heptads, which are required for CTD phase-separation.

New Co(II) complexes of 5-nitroorotate with imidazole or N-methylimidazole co-ligands: Crystal and molecular structures, vibrational spectra and antimicrobial activities

Two novel Co(II) complexes of 5-nitroorotate with imidazole (ImH), [Co(5-NO2HOr)(H2O)2(ImH)2] (1) and N-methylimidazole (N-MeIm), [Co(5-NO2HOr)(H2O)2(N-MeIm)2] (2) have been synthesized and characterized by single crystal X-ray diffraction, PXRD, FT-IR and Raman spectroscopy, as well as elemental and thermal analyses. Both complexes crystallize in the monoclinic system (space group P21/c). The cobalt(II) ion is chelated by the 5-nitroorotate dianion through the carboxylate oxygen (O1) and the deprotonated pyrimidine nitrogen (N1) atoms. Two monodentate co-ligands, (ImH) in (1) or (N-MeIm) in (2), and two water molecules in cis conformation complete a distorted octahedral coordination sphere. Strong intermolecular OH···O and NH···O hydrogen bonds as well as weak NO···π and CH···π interactions, promote the crystal cohesion. The Hirshfeld surface analysis has been performed. Detailed assignment of the characteristic bands in the IR and Raman spectra, along with the thermogravimetric studies, have provided further evidence for the nature of bonding in these compounds. Additionally, both complexes have been investigated in vitro for their activity against selected bacteria: Gram-negative (E. coli ATCC 11229, P. aeruginosa ATCC 27853), Gram-positive (S. aureus ATCC 6538), and yeast (C. albicans ATCC 10231) under aerobic conditions. Moreover, their activity against bacteria that can constitute pathogens (E. coli ATCC 11229) or the probiotic strain (L. rhamnosus GG) has been tested under anaerobic conditions.

Conformational Switching of A Nano-Size Urea-bridged Zn(II)Porphyrin Dimer by External Stimuli.

For the first time, explicit stabilization of all the three conformers, viz. (cis,cis), (cis,trans) and (trans,trans), of a 'nano-sized' highly-flexible urea-bridged Zn(II)porphyrin dimer have been achieved via careful manipulations of external stimuli such as solvent dielectrics, temperature, anionic interactions, axial ligation and surface-induced stabilization. The conformers differ widely in their structures, chemical and photophysical properties and thus have vast potential applicability. X-ray structural characterizations have been reported for the (cis,cis) and (cis,trans)-conformers. While (cis,cis) conformer stabilized exclusively in dichloromethane, more polar solvents resulted in the stabilization of (cis,trans) and (trans,trans)-conformers. Low temperature promotes the stabilization of (cis,trans)-conformer while rise in temperature facilitates flipping to the (cis,cis) one. Significantly, exclusive stabilization of the (trans,trans)-isomer has been illustrated using acetate anion which facilitates H-bonding with the two amide linkages of the urea spacer. Remarkably, HOPG surface facilitates stabilization of the energetically challenging (trans,trans)-conformer via CH···p and p···p interactions with the solid surface to the porphyrinic cores. DFT calculations demonstrate that the relative stability of the conformers can be modulated upon slight external perturbations as also observed in the experiment. Several factors contributing towards the conformational landscape for the highly flexible urea-bridged porphyrin dimers have been mapped.

An integrative characterization of proline cis and trans conformers in a disordered peptide

Intrinsically disordered proteins (IDPs) often contain proline residues that undergo cis/trans isomerization. While molecular dynamics (MD) simulations have the potential to fully characterize the proline cis and trans subensembles, they are limited by the slow timescales of isomerization and force field inaccuracies. NMR spectroscopy can report on ensemble-averaged observables for both the cis-proline and trans-proline states, but a full atomistic characterization of these conformers is challenging. Given the importance of proline cis/trans isomerization for influencing the conformational sampling of disordered proteins, we employed a combination of all-atom MD simulations with enhanced sampling (metadynamics), NMR, and small-angle x-ray scattering (SAXS) to characterize the two subensembles of the ORF6 C-terminal region (ORF6CTR) from SARS-CoV-2 corresponding to the proline-57 (P57) cis and trans states. We performed MD simulations in three distinct force fields: AMBER03ws, AMBER99SB-disp, and CHARMM36m, which are all optimized for disordered proteins. Each simulation was run for an accumulated time of 180–220 μs until convergence was reached, as assessed by blocking analysis. A good agreement between the cis-P57 populations predicted from metadynamic simulations in AMBER03ws was observed with populations obtained from experimental NMR data. Moreover, we observed good agreement between the radius of gyration predicted from the metadynamic simulations in AMBER03ws and that measured using SAXS. Our findings suggest that both the cis-P57 and trans-P57 conformations of ORF6CTR are extremely dynamic and that interdisciplinary approaches combining both multiscale computations and experiments offer avenues to explore highly dynamic states that cannot be reliably characterized by either approach in isolation.

5-(Pyridin-3-yl)-3,4-dihydro-2H-furan-1-ium (NNKFI): a computational study of its physico-chemical properties.

Recent work on the diazonium ion metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNKDI) suggests that 5-(pyridin-3-yl)-3,4-dihydro-2H-furan-1-ium (NNKFI) may form from NNKDI via an intramolecular reaction. NNKDI is an important carcinogen whose role as an alkylating agent has received significant attention. While there is some experimental evidence supporting NNKFI's production in vitro, it has not yet been directly observed. Little is known about NNKFI's structure and reactivity. We report the first in silico examination of this ion. Our study utilized Kohn-Sham density functional theory (B3LYP/6-311G**) and coupled cluster theory (CCSD/6-31G*) to produce energy-optimized structures, vibrational normal modes and molecular orbitals for NNKFI. To gain insight into the chemical properties of this species, we calculated electrostatic potential surfaces, natural population analysis charges and local Fukui indices. We report data and results for NNKFI's cis and trans conformers. Our work confirms C5 as the preferred site for nucleophilic attack in NNKFI. Stretching motions and predicted bond lengths near O1 are consistent with a somewhat weakened carbonyl structure in this ion. Partial charges, electrostatic potential surfaces and local Fukui indices reveal delocalization of cationic charge on the furanium moiety and notable carbocation character at C5.

Investigation of the expression of Cis P-tau and Pin1 proteins following air pollution induction in the brain tissue of C57BL/6 mice.

Alzheimer's disease (AD) is a multifactorial disease in which environmental factors play a role. Among environmental factors, air pollution is a vital issue in modern life. Despite extensive considerations, it remains uncertain how pollution mediates neurodegeneration in AD. Beta-amyloids and hyperphosphorylated tau proteins are the two main pathological markers that have been studied in AD so far. Tau protein is basically a phosphoprotein whose functions are controlled by phosphorylation. The function of tau protein is to be located on the surface of microtubules and stabilize them. Studies have shown that phosphorylated tau protein (p-tau) exists in cis and trans conformations at Thr231, among which cis is highly neurotoxic. The Pin1 enzyme performs the conversion of cis to trans or vice versa. In this study, an experimental mouse model was designed to investigate the formation of cis p-tau by inducing air pollution. In this way, mice were randomly exposed to pollution at 2-week, 1-month, and 2-month intervals. We investigated the formation of phosphorylated cis tau form during air pollution on mouse brains using Western blots and immunofluorescence. The fluorescent imaging results and Western blotting analysis of mouse brains revealed a significant accumulation of cis p-tau in pollution-treated mice models compared to the healthy control mice. According to Western blot results, air pollution induction caused a significant decrease in Pin1 protein. The results clearly show that the tauopathy observed during air pollution is mediated through the formation of cis tau. Our findings unravel tauopathy mysteries upon pollution and would help find a possible therapeutic target to fight the devastating disorder caused by modern life.

Exploring the molecular solvatochromism, stability, reactivity, and non-linear optical response of resveratrol.

This work analyzes the isomerization effects and solvent contributions to the stability, electronic excitations, reactivity, and non-linear optical properties (NLO) of resveratrol molecules within the formalism of the Density Functional Theory. The findings suggest that resveratrol solvatochromism is significantly influenced by solvent polarization. The electronic and free energies (E and G) indicate that trans is the most stable conformer. The system is classified as a strong nucleophile. However, the analysis of the Fukui functions and the Mulliken charges indicate that cis-trans isomerization jointly affects the reactive indices of the carbon and hydrogen atoms. The results also suggest that solvent is relevant to solvatochromism and the NLO response. Both cis and trans conformers present strong excitations that undergo a visible hypsochromic change when the polarity of the solvent increases. Once the absorption spectra are connected to the first hyperpolarization ( ) by the Oudar and Chemla relation, the hypsochromism of resveratrol is the reason for the drop in the generation of the second harmonic when the ambient polarity decreases. The CAM-B3LYP DFT results suggest that resveratrol is interesting for NLO applications. Depending on the choice of solvent, values 50 times those observed for urea ( esu), which is a standard NLO material. The optimized geometries of cis and trans isomers of resveratrol in vacuum were obtained using Density Functional Theory (DFT) with the hybrid exchange-correlation function (CAM-B3LYP) and Pople basis set functions, specifically 6-311++G(d,p). The solvent effect on the geometries of both isomers was included using the polarizable continuum model (PCM) with the same level of QM calculation. Vibrational analysis was conducted to confirm that all optimized geometries correspond to the minimum energy. Various electronic properties, including dipole moments, molecular orbitals, transition energy, dipole polarizabilities, and global reactivity parameters, were calculated using both continuum and discrete solvation models based on the sequential QM/MM methodology. All QM calculations were performed with the Gaussian 09 program and the MC simulations with the DICE program. All NLO analysis was carried out using the Multiwfn code.

Close Packing in Trans Conformers Promotes the Formation of Supramolecular Structures with C1 Symmetry.

Assemblies with C1 symmetry exhibit important applications in many fields such as enantioselective catalysis. However, their formation is challenging due to their large entropic disadvantage, and molecular information on their formation dynamics is limited because of the lack of effective characterization techniques. Here, using achiral amphiphilic molecules such as N-oleoyl ethanolamide (OEA) and its analogues as modeling assembly units, we demonstrated that the sss polarization signals, generated by femtosecond sum frequency generation vibrational spectroscopy (SFG-VS), provide a powerful tool to monitor the formation dynamics of the C1 symmetric supramolecular structures at the interfaces. The trans conformation of the assembly units can provide strong π-π interactions and thus produce enough enthalpy to drive the formation of C1 symmetric supramolecular structures. However, the cis conformation impedes the assembly of C1 symmetric structures and cannot generate sss and chiral polarization SFG signals. These findings may aid in rationally constructing ordered and functional superstructures and understanding the mechanism of chirality formation.

Neutral and cation 1,2-dichloropropane molecular structures and energies investigated by DFT and ab initio methods

A theoretical investigation on the molecular structures of the isolated 1,2-dichloropropane (C3H6Cl2) neutral and its molecular cation was performed using high levels of density functional theory and ab initio methods. Three stable structural conformers have been found for the neutral molecule, with the Trans conformation being the most stable by about 5.8 kJ/mol on average in comparison with the (+) Gauche and (−) Gauche conformations. As for the molecular cation, five stable conformational structures have been determined with energy differences within about 25 kJ/mol, and with the (−) Near Cis conformer being the most stable cation species. The computed vibrational frequencies were compared with experimental values and the main IR spectral features assigned. The theoretical first adiabatic ionization energy of has been determined as 10.69 ± 0.05 eV, from the corresponding neutral and cation molecular energies, via ab initio composite methods, and is in good agreement with the experimental value from photoelectron spectroscopy.

A few examples of cis trans isomerization in complexes involving the oxamide function

Synthesis of heterodinuclear 3d transition metal complexes in which two metal ions are introduced in equivalent coordination sites of a ligand is quite uncommon. We have previously shown that the application of the cis–trans isomerization of the oxamido group was able to furnish such a possibility. In the present paper we demonstrate that this synthetic pathway, relying on the possibility of changing the conformation (cis vs trans) of the oxamido group, can be extended to other ligands. Although we have not been able to characterize these complexes by structural determinations, FAB-MS, EPR and magnetic data do confirm the efficiency of this reaction pathway. We also demonstrate that the cis–trans isomerization of the oxamido group is not due to a particular property of the ion involved in the reaction. In fact, isomerization is governed by the basicity of the reaction medium. According to the reaction condition, it is possible to favor or not this phenomenon, and to increase the accessibility to a larger number of novel genuine complexes. But the oxophilic character of the lanthanide ions limits the use of this synthetic pathway because it impedes this isomerization. Eventually, the very weak magnetic interactions observed in these Cu-Gd complexes can be explained thanks to spin polarization.

Electrochemical stability of low viscosity ion-pair electrolytes: Structure and interaction in quaternary ammonium-based Ionic liquid containing bis(trifluoromethylsulfonyl)imide anion and analogue

Quaternary ammonium-based ionic liquids (QAIL) consist of an aliphatic cation and possess characteristic properties different from those of aromatic (like imidazolium) with extensive cited applications. The redox stability of QA cations has attractively nominated them to achieve static and dynamic electrochemical phenomena. Herein, we investigated the influence of various anions (bis(fluorosulfonyl)imide [FSI]− and bis(trifluoromethylsulfonyl)imide [NTf2]−) on the structure, electronic, and electrochemical properties of low-viscosity ILs comprising QA cation (triethylpentyl ammonium [N2225]+) by employing highly versatile empirical exchange-correlation functional M06–2X in the context of density functional theory (DFT). The electronic structure, cation-anion interaction energy, dipole moment, cation-anion charge transfer, cathodic and anodic potential boundaries, electrochemical window (ECW), and density of state (DOS) were calculated and discussed. Liquid state studied by polarizable continuum model (PCM). The thermodynamics cycle method, an alternative to HOMO/LUMO method, was used to predict ECW's more realistic. ECWs for [N2225][FSI] ≥ [N2225][NTf2] were found to be wider than the experimental imidazolium counterpart by about two volts. [FSI]− anion is overwhelmingly involved in charge transfer with the cation compared to [NTf2]−. The more redox-stable [N2225][FSI] IL is expected to have less corrosive effects with metal electrodes because the anion (1) cis conformer takes a particular orientation relative to the cation, (2) has a higher charge transfer, and (3) F's atoms have a higher occupation number than [N2225][NTf2] IL. Therefore, these results provide insight for further investigation to expand the electrochemical application of redox-stable aliphatic QAILs involving the two targeted anions.

A tethering mechanism underlies Pin1-catalyzed proline cis-trans isomerization at a noncanonical site.

The prolyl isomerase Pin1 catalyzes the cis-trans isomerization of proline peptide bonds, a non-covalent post-translational modification that influences cellular and molecular processes, including protein-protein interactions. Pin1 is a two-domain enzyme containing a WW domain that recognizes phosphorylated serine/threonine-proline (pS/pT-P) canonical motifs and an enzymatic PPIase domain that catalyzes proline cis-trans isomerization of pS/pT-P motifs. Here, we show that Pin1 uses a tethering mechanism to bind and catalyze proline cis-trans isomerization of a noncanonical motif in the disordered N-terminal activation function-1 (AF-1) domain of the human nuclear receptor PPARγ. NMR reveals multiple Pin1 binding regions within the PPARγ AF-1, including a canonical motif that when phosphorylated by the kinase ERK2 (pS112-P113) binds the Pin1 WW domain with high affinity. NMR methods reveal that Pin1 also binds and accelerates cis-trans isomerization of a noncanonical motif containing a tryptophan-proline motif (W39-P40) previously shown to be involved in an interdomain interaction with the C-terminal ligand-binding domain (LBD). Cellular transcription studies combined with mutagenesis and Pin1 inhibitor treatment reveal a functional role for Pin1-mediated acceleration of cis-trans isomerization of the W39-P40 motif. Our data inform a refined model of the Pin1 catalytic mechanism where the WW domain binds a canonical pS/T-P motif and tethers Pin1 to the target, which enables the PPIase domain to exert catalytic cis-trans isomerization at a distal noncanonical site.

High resolution far-infrared synchrotron spectroscopy of 2-furfural conformers: Fundamental and hot bands.

In the continuity of a previous jet-cooled rovibrational study of trans and cis conformers of 2-furfural in the mid-infrared region (700-1750cm-1) [Chawananon et al., Molecules 28 (10), 4165 (2023)], the present work investigates the far-infrared spectroscopy of 2-furfural using a long path absorption cell coupled to a high-resolution Fourier transform spectrometer and synchrotron radiation at the AILES beamline of the SOLEIL synchrotron. Guided by anharmonic calculations, vibrational energy levels and excited-state rotational constants are sufficiently predictive for a complete assignment of all fundamental and combination bands up to 700cm-1, as well as the rovibrational analysis of 4 (1) low-frequency modes of trans-(cis-)2-furfural. A global rovibrational simulation, including far-infrared rovibrational lines and microwave and millimeter-wave rotational lines assigned in a previous study [Motiyenko et al., J. Mol. Spectrosc., 244, 9 (2007)] provides a reliable set of ground- and excited-state rotational parameters involving ring torsion, bending, and ring puckering modes of 2-furfural. In a second step, a rovibrational analysis of several hot band sequences, mainly involving the lowest frequency ring CHO torsion mode, is carried out. Reliable values of some anharmonic coefficients are obtained experimentally and could serve as a benchmark for validating advanced anharmonic calculations related to these large amplitude motions of flexible molecules.

Structural insights into ligand recognition and activation of the succinate receptor SUCNR1

Succinate, a citric acid cycle intermediate, serves important functions in energy homeostasis and metabolic regulation. Extracellular succinate acts as a stress signal through succinate receptor (SUCNR1), a class A G protein-coupled receptor. Research on succinate signaling is hampered by the lack of high-resolution structures of the agonist-bound receptor. We present cryoelectron microscopy (cryo-EM) structures of SUCNR1-Gi complexes bound to succinate and its non-metabolite derivative cis-epoxysuccinate. Key determinants for the recognition of succinate in cis conformation include R2817.39 and Y832.64, while Y301.39 and R993.29 participate in the binding of both succinate and cis-epoxysuccinate. Extracellular loop 2, through F175ECL2 in its β-hairpin, forms a hydrogen bond with succinate and caps the binding pocket. At the receptor-Gi interface, agonist binding induces the rearrangement of a hydrophobic network on transmembrane (TM)5 and TM6, leading to TM signaling through TM3 and TM7. These findings extend our understanding of succinate recognition by SUCNR1, aiding the development of therapeutics for the succinate receptor.

Pin1-catalyzed conformational regulation after phosphorylation: A distinct checkpoint in cell signaling and drug discovery.

Protein phosphorylation is one of the most common mechanisms regulating cellular signaling pathways, and many kinases and phosphatases are proven drug targets. Upon phosphorylation, protein functions can be further regulated by the distinct isomerase Pin1 through cis-trans isomerization. Numerous protein targets and many important roles have now been elucidated for Pin1. However, no tools are available to detect or target cis and trans conformation events in cells. The development of Pin1 inhibitors and stereo- and phospho-specific antibodies has revealed that cis and trans conformations have distinct and often opposing cellular functions. Aberrant conformational changes due to the dysregulation of Pin1 can drive pathogenesis but can be effectively targeted in age-related diseases, including cancers and neurodegenerative disorders. Here, we review advances in understanding the roles of Pin1 signaling in health and disease and highlight conformational regulation as a distinct signal transduction checkpoint in disease development and treatment.

New line list for the ν4 bands of the trans (790.117 cm–1) and cis (851.943 cm–1) conformers of nitrous acid (HONO): Accurate positions and absolute intensities

The goal of this work was to update and significantly improve the line lists that have been generated recently for 11 µm bands of the trans- and cis- conformer forms of nitrous acid (HONO) [Armante R, Perrin A, Kwabia Tchana F, Manceron L. The ν4 bands at 11 μm: linelists for the trans- and cis- conformer forms of nitrous acid (HONO) in the 2019 version of the GEISA database. Molecular Physics 2021;120:e1951860]. That 2019 version of the 11 µm line list was generated using the spectroscopic parameters that were available, at that time, in the literature. During the present study, we used high-resolution Fourier transform spectra recorded at 11 µm to perform a large investigation of line positions and intensities for the ν4 bands of the trans- and cis-conformer of HONO. The resulting set of experimental ν4 (absolute) intensities and of 41 energy levels were used to determine, by least squares fit computations, improved position and intensity parameters for the ν4 bands of the trans- and cis-conformer of HONO. For trans-HONO, the ν4 band appeared not to be perturbed, while for cis-HONO a weak high order B-type Coriolis, coupling together the 41 and 61 energy levels was evidenced for the first time. This new list is of potential interest for the IASI-NG (Infrared Atmospheric Sounding Interferometer - New Generation) instrument which will be launched on board the METOP-SG satellite in 2025.

Photo-transformations of 2-aminothiazole-4-carboxylic acid in low-temperature matrices

The structure, spectroscopic properties and photo-induced conformational changes of 2-aminothiazole-4-carboxylic acid (ACA) isolated in argon and nitrogen matrices were studied using matrix-isolation FTIR spectroscopy and DFT calculations undertaken at the B3LYPD3/6–311++G(3df,3pd) level of theory. Out of 18 stable isomers, the three most stable structures with the five-membered ring stabilized by two C=C and C=N double bonds and with different arrangement of the carboxyl group were identified in both matrices after deposition. Conformer ACA1 has trans and conformers ACA2 and ACA3 have cis conformation of the COOH group and the calculated abundance of 69.5%, 18.2% and 12.2%, respectively. Following irradiation at 285 nm, a rotation of the OH group around the C–O bond in ACA1 was detected leading to increase of ACA2. The corresponding reverse photo-rotamerization was detected at 296 nm, resulting in the recovery of the initial isomer ACA1. Upon NIR irradiation a dominant process was rotamerization within the carboxylic group leading to changes in the population of the ACA1 trans and ACA2 cis forms.

Multi-methodological analysis of hydrogen desorption from graphene

Chemisorption of hydrogen on graphene has been extensively investigated in last decades, but the reported values of over several eV, depending on different factors, such as the local structural environment, substrates or previously bound hydrogen.In this work, we combine Temperature-Programmed Desorption experiments with simulations using empirical reactive force fields and Density Functional Theory calculations. We observe that desorption occurs through processes with different activation energies, which we are able to identify by analyzing simulation data and post-processing experimental ones through a procedure based on Arrhenius fit with feedback. The result is the assignment of experimentally observed desorption peaks to different desorption processes, namely desorption from isolated sp3 H, or couples of H in conformation cis or trans, or edge sp3 or sp2 H.The protocol we outline is generally applicable and might be particularly useful in more complex cases with larger multiplicity of desorption peaks.

Pixelated High-Q Metasurfaces for in Situ Biospectroscopy and Artificial Intelligence-Enabled Classification of Lipid Membrane Photoswitching Dynamics.

Nanophotonic devices excel at confining light into intense hot spots of electromagnetic near fields, creating exceptional opportunities for light-matter coupling and surface-enhanced sensing. Recently, all-dielectric metasurfaces with ultrasharp resonances enabled by photonic bound states in the continuum (BICs) have unlocked additional functionalities for surface-enhanced biospectroscopy by precisely targeting and reading out the molecular absorption signatures of diverse molecular systems. However, BIC-driven molecular spectroscopy has so far focused on end point measurements in dry conditions, neglecting the crucial interaction dynamics of biological systems. Here, we combine the advantages of pixelated all-dielectric metasurfaces with deep learning-enabled feature extraction and prediction to realize an integrated optofluidic platform for time-resolved in situ biospectroscopy. Our approach harnesses high-Q metasurfaces specifically designed for operation in a lossy aqueous environment together with advanced spectral sampling techniques to temporally resolve the dynamic behavior of photoswitchable lipid membranes. Enabled by a software convolutional neural network, we further demonstrate the real-time classification of the characteristic cis and trans membrane conformations with 98% accuracy. Our synergistic sensing platform incorporating metasurfaces, optofluidics, and deep learning reveals exciting possibilities for studying multimolecular biological systems, ranging from the behavior of transmembrane proteins to the dynamic processes associated with cellular communication.