Visualization of Recrystallization Induced by Ultraviolet Degradation of a Polypropylene Film Using Raman Imaging

Raman images were constructed for polypropylene (PP) films before and after ultraviolet (UV) irradiation (100 mW, 248-436 nm) for 10 h using several intensity ratios of Raman bands that are sensitive to crystallization of PP. In the images of PP films before the irradiation the intensity ratios are nearly uniform for the films but for those of the PP films after the irradiation, the ratios become large with a mottled pattern, indicating that recrystallization occurs in the PP films upon the irradiation of the UV light. The UV-irradiated PP films show worm-like shaped structures in few micrometer order representing the recrystallization of PP. The temperature gradient of PP is low (273 K), and thus, it is very likely that due to UV energy and polymer fragmentation, PP molecules become more mobile and some parts of molecular chains in amorphous parts of PP molecules lead to their rearrangement and recrystallization. In this study, we demonstrate that Raman imaging clearly detects subtle changes in the crystallinity with a micrometer order structure which morphological images cannot observe.

Patterns of Cross-Peaks in Two-Dimensional Correlation Spectra to Probe Intermolecular Interactions Described by Two Reversible Reactions

Two-dimensional correlation spectroscopy is used to investigate the intermolecular interaction between two substances dissolved in the same solutions, where the intermolecular interaction is described by two reversible reactions producing two supramolecular aggregates. The severe overlappings expected among the characteristic peaks of the original solute and aggregates make conventional one-dimensional spectra difficult to accurately reflect the physiochemical nature of the intermolecular interaction. The double asynchronous orthogonal sample design (DAOSD) approach is utilized to analyze the simulated data for proof-of-principle demonstration. The patterns of cross-peaks are much more complex compared with the intermolecular interaction described by only a single reaction. Four major groups of cross-peaks with characteristic patterns observed in the pair of DAOSD asynchronous spectra are systematically analyzed and classified. Further analysis of the spectral feature of the cross-peaks of the DAOSD asynchronous spectra is helpful to exact additional information concerning the variation of the peak position and peak width of the aggregates compared with those of the original solute. The result is important to reveal the physicochemical nature of intermolecular interaction between the solutes (e.g., changes in conformation, dynamical behavior, etc.). The pattern of cross-peaks in the corresponding 2D asynchronous spectra may become rather complex when the peak position, peak width, and peak intensity of two supramolecular aggregates change simultaneously. Further work using artificial intelligence techniques to interpret the complex cross-peaks is still being carried out.

In-situ surface enhanced Raman spectroscopy revealing the role of metal-organic frameworks on photocatalytic reaction selectivity on highly sensitive and durable Cu-CuBr substrate

Photocatalytic reactions using copper-based nanomaterials have emerged as a new paradigm in green technology. Selective photocatalysis is very important for improving energy utilization efficiency, and in order to directional improve catalytic selectivity, it is necessary to understand the mechanism of interfacial reactions at the molecular level. Therefore, a unique bifunctional Cu-CuBr substrate is first fabricated via an electrochemical method, which overcomes the instability of traditional copper-based materials and endows high surface-enhanced Raman spectroscopy (SERS) sensitivity and photocatalytic performance and can be stored stably for more than a year. Further modification of the surface with Metal-Organic Frameworks (MOFs) containing carboxyl functional groups can significantly tune the surface properties of the substrate. This increases the adsorption of cationic dyes to improve the SERS effect, and 10-10 M methylene blue can easily be detected with this substrate. Surprisingly, in-situ SERS monitoring of the interfacial photocatalytic dehalogenation reaction of aromatic halides through its intrinsic SERS effect reveal two competing selective reaction pathways, self-coupling and hydrogenation. Typically, the SERS spectra reveal that the latter's selectivity was greatly enhanced after MOFs modification, and the yield rate of the hydrogenated product increased from 27.6 % to 46.9 % (selectivity increased from 32.7 % to 51.5 %). This proves that the surface properties of catalysts, especially the affinity for reaction intermediates, can effectively regulate catalytic selectivity.

ATR-far-ultraviolet spectroscopy: a challenge to new σ chemistry

This review reports the recent progress on ATR-far ultraviolet (FUV) spectroscopy in the condensed phase. ATR-FUV spectroscopy for liquids and solids enables one to explore various topics in physical chemistry, analytical chemistry, nanoscience and technology, materials science, electrochemistry, and organic chemistry. In this review, we put particular emphasis on the three major topics: (1) studies on electronic transitions and structures of various molecules, which one cannot investigate via ordinary UV spectroscopy. The combined use of ATR-FUV spectroscopy and quantum chemical calculations allows for the investigation of various electronic transitions, including σ, n-Rydberg transitions. ATR-FUV spectroscopy may open a new avenue for σ-chemistry. (2) ATR-FUV spectroscopy enables one to measure the first electronic transition of water at approximately 160 nm without peak saturation. Using this band, one can study the electronic structure of water, aqueous solutions, and adsorbed water. (3) ATR-FUV spectroscopy has its own advantages of the ATR method as a surface analysis method. ATR-FUV spectroscopy is a powerful technique for exploring a variety of top surface phenomena (∼50 nm) in adsorbed water, polymers, graphene, organic materials, ionic liquids, and so on. This review briefly describes the principles, characteristics, and instrumentation of ATR-FUV spectroscopy. Next, a detailed description about quantum chemical calculation methods for FUV and UV regions is given. The recent application of ATR-FUV-UV spectroscopy studies on electronic transitions from σ orbitals in various saturated molecules is introduced first, followed by a discussion on the applications of ATR-FUV spectroscopy to studies on water, aqueous solutions, and adsorbed water. Applications of ATR-FUV spectroscopy in the analysis of other materials such as polymers, ionic liquids, inorganic semiconductors, graphene, and carbon nanocomposites are elucidated. In addition, ATR-FUV-UV-vis spectroscopy focusing on electrochemical interfaces is outlined. Finally, FUV-UV-surface plasmon resonance studies are discussed.

Attenuated Total Reflection Infrared and Far-Infrared, and Raman Spectroscopy Studies of Minerals, Rocks, and Biogenic Minerals

Attenuated total reflection infrared (ATR-IR, 4000-400 cm-1), ATR-far-IR (ATR-FIR, 400-50 cm-1), and Raman spectra (4000-10 cm-1) were measured for calcium carbonate, three kinds of minerals (calcite, aragonite, and quartz), two kinds of rocks (obsidian and pumice), and four kinds of biogenic minerals, i.e., coral (aragonite), Ruditapes philippinarum (aragonite), Meretrix lusoria (aragonite), and Corbicula japonica (aragonite), to investigate the polymorphism of minerals and biogenic minerals, differences in the crystal structure among aragonite and aragonite biogenic minerals, water in the minerals and biogenic minerals, Boson peaks of obsidian and pumice, very small amounts of carotenoids in the three kinds of shells, and so on. In this study, we put some emphasis on the low-frequency region of IR (FIR) and Raman spectra. ATR-FIR spectra were measured down to 50 cm-1 and Raman spectra were obtained down to 10 cm-1. Second derivative spectra were calculated for the FIR spectra. It has been found from the present study that the FIR spectra are the most powerful for exploring polymorphism and differences in the crystal structure among aragonite and aragonite biogenic minerals. A Boson peak, which is a characteristic low-frequency Raman band for amorphous materials, was observed at around 40 cm-1 in the Raman spectra of obsidian and pumice. The Boson peak of pumice is located at a lower frequency by 12 cm-1 than that of obsidian, indicating that the mean atomic volume of pumice is larger than that of obsidian. The present study has revealed that IR spectra are useful to investigate the amounts and structure of fluid and bound water. Moreover, it has also been found that Raman spectra can detect a very tiny amount of carotenoids in the shells due to the resonance Raman effect.

Visualization and identification of components in a gigantic spherical dolomite concretion by Raman imaging in combination with MCR or CLS methods

The combination of Raman imaging and multivariate curve resolution (MCR) or classical least squares (CLS) has allowed us to explore the distribution and identification of components in a gigantic spherical dolomite concretion. It has been found by the MCR and CLS analyses of imaging data that the concretion contains dolomite, kerogen, anatase, quartz, plagioclase, and carbon materials with considerably large distribution of dolomite. The existence of these components has also been confirmed by the point-by-point analysis of imaging data. The distributions of these components were clearly observed by Raman images. Of note is that the amount of carbon materials is considerably large, and they are buried among the matrix sedimentary grains in the concretion, suggesting that there exist soft tissues with biological origin. Moreover, one of the loading spectra of CLS shows intense bands in the region of 3000-2800 cm-1, and bands at ca. 1658, ca. 1585, 1455, 1323, and 1261 cm-1. These bands indicate the existence of decomposed organic materials in the concretion. Raman imaging of concretions provides direct evidence that concretions are of biological organic origin.

Validation of the cell culture monitoring using a Raman spectroscopy calibration model developed with artificially mixed samples and investigation of model learning methods using initial batch data

The development of calibration models using Raman spectra data has long been challenged owing to the substantial time and cost required for robust data acquisition. To reduce the number of experiments involving actual incubation, a calibration model development method was investigated by measuring artificially mixed samples. In this method, calibration datasets were prepared using spectra from artificially mixed samples with adjusted concentrations based on design of experiments. The precision of these calibration models was validated using the actual cell culture sample. The results showed that when the culture conditions were unchanged, the root mean square error of prediction (RMSEP) of glucose, lactate, and antibody concentrations was 0.34, 0.33, and 0.25 g/L, respectively. Even when variables such as cell line or culture media were changed, the RMSEPs of glucose, lactate, and antibody concentrations remained within acceptable limits, demonstrating the robustness of the calibration models with artificially mixed samples. To further improve accuracy, a model training method for small datasets was also investigated. The spectral pretreatment conditions were optimized using error heat maps based on the first batch of each cell culture condition and applied these settings to the second and third batches. The RMSEPs improved for glucose, lactate, and antibody concentration, with values of 0.44, 0.19, and 0.18 g/L under constant culture conditions, 0.37, 0.12, and 0.12 g/L for different cell lines, and 0.26, 0.40, and 0.12 g/L when the culture media was changed. These results indicated the efficacy of calibration modeling with artificially mixed samples for actual incubations under various conditions.

SERS Tracking Oxidative Stress on a Metalloporphyrin Framework by Vitamin C

Accurate control of charge transfer is crucial to investigate the catalytic reaction mechanism of the biological oxidation process that biomedicine participates in. Herein, we have established an assembly model of metalloporphyrin framework (MPF) nanosheets as the active centers of biological enzymes. The introduction of Vitamin C (VC) into the MPF system can precisely modulate its content of charges. The surface-enhanced Raman scattering activity and peroxidase-like catalytic performance are enhanced simultaneously for the first time by manipulating the optimal molar ratio of an MPF to VC and the reaction sequence with target model molecules. We have confirmed that the formation of the intermediate of Fe(2+)-OOH species is specifically enhanced after VC modulation, which indicates that VC can regulate the oxidative stress of the active center of biological enzymes. This discovery not only accurately resolves the mechanism of VC-selective anticancer therapy but also has important significance for the precise treatment of VC synergistic targeting medicines.

Combined X-ray Reflectivity and Infrared Study of the Effect of Hydrogen Bonding of the OH Group on the Relaxation Behavior in Ultrathin Polyvinylphenol Films on SiO2

Utilizing X-ray reflectivity and infrared reflection absorption spectroscopy (IR-RAS), we have investigated the thermal expansion and contraction of ultrathin polyvinylphenol (PVPh) films supported on a silicon (100) substrate capped with an amorphous SiO2 layer. Despite being known to form strong interactions with the SiO2 surface, the thin PVPh films showed a reduction in the glass-transition point Tg, similar to the behavior of polystyrene thin films deposited on SiO2. We explored the relationship between thermal expansivity and film thickness using well-annealed films and found that it decreases with film thickness in the range below twice the radius of gyration of a polymer chain (2Rg) in the glassy state. Thickness expansion in the glassy state and contraction in thickness at temperatures higher than Tg bulk (melt state) showed the presence of two competing relaxation processes. The reported negative thermal expansion in PVPh thin films, which was discovered to be one of the inherent properties, may have been caused by the fast relaxations that take place at the free polymer surface. IR-RAS was utilized to investigate the effect of thickness on hydrogen bonding in PVPh, and it was confirmed that with decreasing thickness, hydrogen bonding becomes weak, and the number of free OH groups increases. Therefore, thinner PVPh samples exhibit lower Tgs as an effect of easier molecular motions.

Variations in the Protein Hydration and Hydrogen-Bond Network of Water Molecules Induced by the Changes in the Secondary Structures of Proteins Studied through Near-Infrared Spectroscopy

This study investigated how the secondary structural changes of proteins in aqueous solutions affect their hydration and the hydrogen-bond network of water molecules using near-infrared (NIR) spectroscopy. The aqueous solutions of three types of proteins, i.e., ovalbumin, β-lactoglobulin, and bovine serum albumin, were denatured by heating, and changes in the NIR bands of water reflecting the states of hydrogen bonds induced via protein secondary structural changes were investigated. On heating, the intermolecular hydrogen bonds between water molecules as well as between water and protein molecules were broken, and protein molecules were no longer strongly bound by the surrounding water molecules. Consequently, the denaturation was observed to proceed depending on the thermodynamic properties of the proteins. When the aqueous solutions of proteins were cooled after denaturation, the hydrogen-bond network was reformed. However, the state of protein hydration was changed owing to the secondary structural changes of proteins, and the variation patterns were different depending on the protein species. These changes in protein hydration may be derived from the differences in the surface charges of proteins. The elucidation of the mechanism of protein hydration and the formation of the hydrogen-bond network of water molecules will afford a comprehensive understanding of the protein functioning and dysfunctioning derived from the structural changes in proteins.

A new apparatus and the relevant method to retrieve IR spectra of solutes from the corresponding aqueous solutions

An apparatus and relevant approach to obtaining IR spectra of solutes from the corresponding aqueous solution were developed. In the experiment, aqueous solutions were converted into aerosols using an ultrasonic or a pneumatic device. Subsequently, water in the nebulized solution is completely gasified under a high-speed flow and low vacuum environment. Via this process, the aqueous solution changes into a mixture of a solute or solutes and gaseous water, whose single-beam IR spectra are collected. Then, the newly developed RMF (retrieving moisture-free IR spectrum) method and the relevant approach described in our recent papers have been adopted to treat the resultant single-beam sample spectrum. As a result, the spectral contribution of the vibrational-rotational peaks of gaseous water can be removed or significantly attenuated, and IR spectra of solutes can be obtained. The approach shows an obvious advantage in retrieving the IR spectrum of volatile solutes from its aqueous solution. This capability is showcased by obtaining IR spectra of isopropanol and ethyl acetate successfully. IR spectra of these compounds can be retrieved even if the concentration of the solute is below 10 wt%. Moreover, atomization via ultrasonic/pneumatic methods offers a mild way to gasify solutes whose boiling points are remarkably higher than that of water. This advantage is manifested by acquiring IR spectra of 1-butanol and 1,2-propanediol in the gaseous phase under ambient conditions.

Biogenic apatite in carbonate concretions with and without fossils investigated in situ by micro-Raman spectroscopy

Micro-Raman spectra of concretions with and without fossils were measured in a nondestructive manner. The band position and full width at half maximum height (FWHM) of ν1-PO43- of apatite in the concretions were analyzed to investigate the origin of apatite. The analyzed concretions were derived from the Kita-ama Formation of the Izumi Group, Japan. The micro-Raman analysis showed that the apatites in the concretions were divided into two groups: Group W (wide FWHM group) and Group N (narrow FWHM group). The apatite belonging to Group W is suggested to be biogenic apatite originating from the soft body tissues of organisms because the Sr content is high and the FWHM is similar to that of apatite in bones and teeth of present-day animals. The other apatite belonging to Group N is considered affected by the diagenetic process because of its narrow FWHM and F substitution. These features of both groups were observed regardless of the presence of fossils or absence of fossils in the concretions. This Raman spectroscopic study suggests that the apatite at the time of concretion formation belonged to Group W but was changed to Group N by the substitution of F during the diagenesis process.

Real-world treatment patterns and outcomes of abemaciclib for the treatment of HR + , HER2- metastatic breast cancer patients in Japan

INTRODUCTION

This study described, in routine clinical practice in Japan, the patient characteristics, treatment patterns, and outcomes of female patients with HR + /HER2- metastatic breast cancer (MBC) who started abemaciclib treatment.

METHODS

Clinical charts were reviewed for patients starting abemaciclib in 12/2018-08/2021 with a minimum of 3 months follow-up data post-abemaciclib initiation regardless of abemaciclib discontinuation. Patient characteristics, treatment patterns, and tumor response were descriptively summarized. Kaplan-Meier curves estimated progression-free survival (PFS).

RESULTS

200 patients from 14 institutions were included. At abemaciclib initiation, median age was 59 years, and the Eastern Cooperative Oncology Group performance status score was 0/1/2 for 102/68/5 patients (58.3/38.9/2.9%), respectively. Most had an abemaciclib starting dose of 150 mg (92.5%). The percentage of patients receiving abemaciclib as 1st, 2nd, or 3rd line treatment was 31.5%, 25.8%, and 25.2%, respectively. The most frequent endocrine therapy drugs used with abemaciclib were fulvestrant (59%) and aromatase inhibitors (40%). Evaluation of tumor response was available for 171 patients, 30.4% of whom had complete/partial response. Median PFS was 13.0 months (95% CI 10.1-15.8 months).

CONCLUSIONS

In a routine clinical practice setting in Japan, patients with HR + , HER2- MBC appear to benefit from abemaciclib treatment in terms of treatment response and median PFS, with the results broadly reflecting the evidence demonstrated in clinical trials.

A new approach to recognizing the correct pattern of cross-peaks from a noisy 2D asynchronous spectrum by detecting intrinsic symmetry via the Kolmogorov-Smirnov test

The characteristic cluster pattern of cross-peaks in a 2D asynchronous spectrum provides an effective way to reveal the specific physicochemical nature of subtle spectral changes caused by intermolecular interactions. However, the inevitable presence of noise in the 1D spectra used to construct a 2D asynchronous spectrum is significantly amplified, which poses a serious challenge in identifying the correct cluster pattern of the cross-peaks. While mirror symmetry occurs in some types of cross-peaks, it does not occur in other types. The Kolmogorov-Smirnov test provides a statistical means to check whether the mirror symmetry exists or not between a pair of cross-peaks covered by heavy noise. Thus, different types of cross-peak clusters can be distinguished by excavating intrinsic spectral features from the noisy 2D asynchronous spectrum. The effectiveness of this approach in investigating the nature of intermolecular interactions was showcased in both a simulated model system and a real artemisinin/N-methyl pyrrolidone system.

Development of Raman Calibration Model Without Culture Data for In-Line Analysis of Metabolites in Cell Culture Media

In this study, we developed a method to build Raman calibration models without culture data for cell culture monitoring. First, Raman spectra were collected and then analyzed for the signals of all the mentioned analytes: glucose, lactate, glutamine, glutamate, ammonia, antibody, viable cells, media, and feed agent. Using these spectral data, the specific peak positions and intensities for each factor were detected. Next, according to the design of the experiment method, samples were prepared by mixing the above-mentioned factors. Raman spectra of these samples were collected and were used to build calibration models. Several combinations of spectral pretreatments and wavenumber regions were compared to optimize the calibration model for cell culture monitoring without culture data. The accuracy of the developed calibration model was evaluated by performing actual cell culture and fitting the in-line measured spectra to the developed calibration model. As a result, the calibration model achieved sufficiently good accuracy for the three components, glucose, lactate, and antibody (root mean square errors of prediction, or RMSEP = 0.23, 0.29, and 0.20 g/L, respectively). This study has presented innovative results in developing a culture monitoring method without using culture data, while using a basic conventional method of investigating the Raman spectra of each component in the culture media and then utilizing a design of experiment approach.

Toward a New Era of SERS and TERS at the Nanometer Scale: From Fundamentals to Innovative Applications

Surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS) have opened a variety of exciting research fields. However, although a vast number of applications have been proposed since the two techniques were first reported, none has been applied to real practical use. This calls for an update in the recent fundamental and application studies of SERS and TERS. Thus, the goals and scope of this review are to report new directions and perspectives of SERS and TERS, mainly from the viewpoint of combining their mechanism and application studies. Regarding the recent progress in SERS and TERS, this review discusses four main topics: (1) nanometer to subnanometer plasmonic hotspots for SERS; (2) Ångström resolved TERS; (3) chemical mechanisms, i.e., charge-transfer mechanism of SERS and semiconductor-enhanced Raman scattering; and (4) the creation of a strong bridge between the mechanism studies and applications.

Comprehensive modified approaches to reducing the interference of moisture from an FTIR spectrum and the corresponding second derivative spectrum

We proposed a modified and improved approach to removing the interference of moisture from an IR spectrum and the corresponding second derivative spectrum. The temperature fluctuation in the air of the optical path and baseline-drift lead to the small but persistent presence of the interference of moisture. The problem has been successfully addressed by adopting a double-matching strategy. Additionally, two-dimensional correlationspectra (2D-COS) are generated using the second derivative or third derivative spectrum of the negative base 10 logarithms of the single-beam spectra, thereby removing the linear slope or quadratic portion of baseline-drift. Using the newly adopted approach, the residual interferences of moisture are attenuated. We applied the new approach to the IR spectra and the second derivative spectra of neat hexadecanol and biaxially oriented polypropylene (BOPP) film, and some promising preliminary results are obtained. In hexadecanol, two highly overlapping peaks at 1464 and 1463 cm^-1 are revealed. In BOPP, the envelope at 1458 cm^-1 is found to be composed of a number of sub-peaks.

Homogeneous Pt nanostructures surface functionalized with phenylboronic acid phosphonic acid derivatives as potential biochemical nanosensors and drugs: SERS and TERS studies

Here, surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS) were used to characterize the selective adsorption of N-substituted 4-[(NH-R)(phosphono)-S-methyl]phenylboronic acids on the surface of platinum nanoparticles (PtNPs) from an aqueous solution and from air. The nature of the interaction of the studied compounds with the PtNPs/H₂ O and PtNPs/air interfaces was discussed and compared. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA-PA) and its two analogs (2-PBA-PA and bis{1-PBA-PA}) as well as the PtNPs were synthesized in surfactant/ion-free solution via a synthetic route that allows control of the size and morphology of the NPs. The positively charged PtNPs with a size of ~12 nm were characterized by ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD).

Morphological and clinical implications of the optical coherence tomography-derived lipid core burden index

Background

Intracoronary optical coherence tomography (OCT) is a valuable tool for vulnerable plaque assessment and morphology-guided risk stratification. However the groundbreaking impact of OCT in clinical practice may be offset by its inherent limitation, the subjectivity in plaque interpretation. Recent studies reported a semi-automated method to assess fibrous cap thickness but data regarding an automated assessment of lipid component at OCT, such a lipid core burden index (LCBI), are lacking.

Purpose

The aim of this study was to assess the morphological characteristics and prognostic implications of an OCT-derived LCBI (OCT-LCBI).

Methods

In order to assess OCT-LCBI in 1003 patients with 1-year follow-up from the CLIMA multicenter registry (clinicaltrial.gov identifier NCT02883088) we used a novel previously validated software able to automate obtain a maximum OCT-LCBI in 4 mm (maxOCT-LCBI4mm). A maxOCT-LCBI4mm cut-off of 400 was used, based on previous literature on this topic. Primary composite clinical endpoint included cardiac death, myocardial infarction and target vessel revascularization. A secondary analysis using clinical outcomes of CLIMA study was performed.

Results

Patients with a maxOCT-LCBI4mm ≥400 showed higher prevalence of fibrous cap thickness <75μm (FCT, odds ratio [OR] 1.43, 95% confidence interval [CI] 1.03–1.99; p=0.034), lipid pool arc >180°(OR 3.93, 95% CI 2.97–5.21; p<0.001), minimum lumen area <3.5 mm2 (OR 1.5, 1.16–1.94; p=0.002), macrophage infiltration (OR 2.38, 95% CI 1.81–3.13; p<0.001) and intra-plaque intimal vasculature (OR 1.34, 95% CI 1.05–1.72, p=0.021). A maxOCT-LCBI4mm ≥400 predicted the primary endpoint (adjusted hazard ratio [HR] 1.86, 95% CI 1.1–3.2; p=0.019) as well as the CLIMA endpoint (HR 2.56, 95% CI 1.24–5.29; p=0.011). Patients with high lipid content and thin FCT <75 μm were at higher risk for adverse events (HR 4.88, 95% CI 2.44–9.72; p<0.001) (Figure 1).

Conclusions

We applied for the first time in a large population with clinical follow-up a software able to automatically obtain a maxOCT-LCBI4mm. A high maxOCT-LCBI4mm was related to vulnerable plaque features and further clinical events. This study represents a step further towards a comprehensive automated assessment of the coronary plaque risk profile.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Supported by a grant from the Centro per la Lotta contro l'Infarto – Fondazione Onlus, Rome, Italy

Retrieving Spectra of Pure Components from the DOSY-NMR Experiment via a Comprehensive Approach Involving the 2D Asynchronous Spectrum, 2D Quotient Spectrum, and Genetic Algorithm Refinement

When diffusion coefficients of different components in a mixture are similar, NMR spectra of pure individual components are difficult to be obtained via a diffusion-ordered spectroscopy (DOSY) experiment. Two-dimensional correlation spectroscopy (2D-COS) is used to analyze the data from the DOSY experiment. Through the properties of the systematic absence of cross-peak (SACP) in the 2D asynchronous spectra, spectra of pure components can be obtained even if their diffusion coefficients are similar. However, fluctuations in peak-position and peak-width are often unavoidable in NMR spectra, which makes SACPs unrecognizable. To address the problem, a 2D quotient spectrum is used to identify the masked SACPs. However, undesirable interference peaks due to the fluctuations in peak-position and peak-width are still present when we extract a spectrum of a component by slicing the 2D asynchronous spectrum across the SACP. A genetic algorithm (GA) is used to select a suitable subset of spectra where the diversities of peak-position and peak-width are significantly reduced. Then, we used the selected spectra to construct a refined 2D asynchronous spectrum so that the spectra of pure components with significant attenuated interference can be obtained. The above approach has been proven to be effective on a model system and a real-world example, demonstrating that 2D-COS possesses a bright perspective in the analysis of the bilinear data from DOSY experiments.

A Study of C=O…HO and OH…OH (Dimer, Trimer, and Oligomer) Hydrogen Bonding in a Poly(4-vinylphenol) 30%/Poly(methyl methacrylate) 70% Blend and its Thermal Behavior Using Near-Infrared Spectroscopy and Infrared Spectroscopy

Inter- and intramolecular hydrogen bonding and their temperature-dependent changes in a poly(4-vinylphenol)/poly(methyl methacrylate)(PVPh 30%/PMMA 70%) blend were investigated using near-infrared (NIR) and infrared (IR) spectroscopy. Band assignments of the fundamentals and first overtones of the OH stretching mode of a free OH group and OH groups in C=O···HO and OH···OH (dimer, trimer, and oligomer) hydrogen bonding of PVPh 30%/PMMA 70% were carried out by comparison between its NIR and IR spectra and comparison with NIR and IR spectra of phenol. The comparison of the NIR spectra of the PVPh 30%/PMMA 70% blend (hereafter, we denote it as PVPh30%) with the corresponding IR spectra reveals that to observe bands arising from the free OH and OH···OH dimer, which is a weaker hydrogen bonding, NIR is better while to investigate bands originating from OH groups in the OH···O=C and OH···OH (oligomer) hydrogen bonds, which are stronger hydrogen bonding, IR is better. Thus, a combination of IR and NIR spectroscopy has provided convincing results for the hydrogen bonding of PVPh30%. The relative intensity of the two bands at 7058 and 6921 cm^-1 (I₇₀₅₈/I₆₉₂₁) due to the first overtones of the OH stretching modes of the free OH group and the OH group in the dimer, respectively, increases significantly above 90 °C, which is close to Tg of PVPh. In concomitance with the intensity increase in the relative intensity of the free OH band, the intensity of a band at 1706 cm^-1 due to the C=O stretching mode of the C=O···HO hydrogen bond of PVPh30% decreases above 90°C. These results suggest that above the Tg of PVPh the C=O···HO hydrogen bond is broken gradually and that the free OH increases. Of note is that below Tg the intensities of NIR bands due to the OH first overtones of free OH group and OH groups in the OH···OH dimer gain intensity in parallel with temperature increase, and above Tg the intensity of the band derived from the OH···OH group increases linearly much slower than that of the band due to the free OH. Moreover, a band due to an OH···OH oligomer decreases linearly. Hence, it is very likely that the OH···OH oligomers dissociate into free OH groups. Anharmonicity of O-H bonds, which is sensitive to a hydrogen bond, was estimated for the free OH and OH bonds in the C=O···HO and OH···OH (dimer, trimer, and oligomer) hydrogen bonding by comparison between the NIR and IR spectra in the OH stretching band regions.

Attenuated Total Reflection Far-Ultraviolet (ATR-FUV) Spectroscopy is a Sensitive Tool for Investigation of Protein Adsorption

Attenuated total reflection far-ultraviolet (ATR-FUV) spectra in the 145-250 nm region were studied for four kinds of proteins (two α-helix-rich proteins: bovine serum albumin (BSA) and lysozyme and two β-sheet rich proteins: concanavalin A and γ-globulin) in different solutions (pure water and phosphate buffered saline, or PBS) with different concentrations. All the spectra show a band at 191 nm due to the π-π^* transition of amide bonds of the proteins. The wavelength of the band does not change with their second structures, suggesting that the corresponding electronic transition mode is localized and polarized in the direction that is not affected by the difference in the peptide folding. The intensity of the 191 nm band differs with the concentration of salt in the solution, suggesting that the band intensity reflects the adsorption density of a protein on the internal reflection element (IRE) made of a sapphire glass prism. According to the intensity changes of the band at 191 nm, it is revealed that the properties in adsorption are different from one protein to another. It is assumed that there are two types of forces on the protein adsorption: one is that among the molecules and the other is that between a molecule and a substrate. The origin of force includes localized electrostatic polarity and affinity to water. The ions in the solvent give a marked effect on these forces, resulting in the difference in the response to adsorption density against the salt concentration in the solvent.

Association and solubility of chlorophenols in CCl4: MIR/NIR spectroscopic and DFT study

This work provides new information on the effect of position and number of substituents on association and solubility of chlorophenols in CCl₄. Using MIR and NIR spectroscopy we examined solutions of 12 chlorophenols at several concentrations. In addition, we calculated (DFT) theoretical spectra and structures of monomers and associates of chlorophenols from dimer to tetramer. The number of substituents at positions 2 and 6 allows to divide studied chlorophenols into three Groups: I (3; 4; 3,4; 3,5), II (2; 2,3; 2,4; 2,5; 2,4,5), and III (2,6; 2,4,6; 2,3,4,5,6). An equilibrium between intermolecular OH⋅⋅⋅OH and intramolecular OH⋅⋅⋅Cl hydrogen bonding depends on position and number of substituents. The extent of association decreases in going from Group I to Group III due to growing steric hindrance near the OH group and the resonance effect from Cl. In chlorophenols of Group I, Cl at positions 3 or 5 weakens the OH⋅⋅⋅OH intermolecular hydrogen bonding, while for Group II it strengthens the OH⋅⋅⋅⋅Cl intramolecular bonding. In contrast, Cl at position 4 has minor effect on association. In the case of Group I, increasing concentration shifts the equilibrium towards solute-solute interactions, whereas for Groups II and III dominate the species with intramolecular OH⋅⋅⋅Cl bonding. The theoretical calculations predict that for monosubstituted chlorophenols of Group I the most stable are non-planar cyclic tetramers, while for disubstituted ones, the non-planar cyclic tetramers and linear trimers have similar binding energies. Chlorophenols of Group II prefer the cyclic non-planar trimers, whereas those of Group III form the planar dimers with an antiparallel orientation of the OH groups. Our study reveals that chlorophenols creating the cyclic associates are better soluble in CCl₄ as compared with those forming the linear ones. Hence, one can conclude that in an inert or weakly interacting solvents the solubility is closely related to the structure of the solute associates.

Random swapping, an effective and efficient way to boost the intensities of cross peaks in a 2D asynchronous spectrum

Analysis of mixture via chromatographic-spectroscopic and analogous experiments is a common task in analytical chemistry. A 2D/nD asynchronous spectrum is effective in retrieving spectra of pure substances even if different components cannot be separated. However, noise in the 2D/nD asynchronous spectrum becomes a bottleneck in the analysis. Finding a suitable sequence of the 1D spectra used in constructing the 2D/nD asynchronous spectrum is helpful to improve the signal-to-noise level. A 2D/nD asynchronous spectrum is often produced via a large number of 1D spectra. The resultant colossal number of the possible sequences makes stochastic search the only possible way to find a suitable sequence. Random changing (RC) and random swapping (RS) are two ways to obtain a new sequence. We found that the possibility of finding a better sequence via an RS is significantly higher than that via an RC in the advanced stage of stochastic searching. This is the reason why the performance of RS is superior to that of RC in two model systems where 2D asynchronous spectra are used. We applied the RS approach on the analysis of water/isopropanol mixtures, and satisfactory sequences are acquired with affordable computational cost. Thus, the RS approach brings about an opportunity increase the signal-to-noise level of a 2D asynchronous spectrum in the analysis of the bilinear data from complex mixed samples.

In situ SERS monitoring of intracellular H2O2 in single living cells based on label-free bifunctional Fe3O4@Ag nanoparticles

Visualization of signaling molecules in single living cells is crucial for understanding cellular metabolism and physiology, which can provide valuable insights into early diagnoses and treatments of diseases. Highly sensitive in situ monitoring of intracellular analytes released from single living cells by virtue of label-free nanosensors is urgently needed, which can avoid interferences from molecular labeling. Here, we proposed an ultrasensitive strategy for in situ imaging of intracellular H₂O₂ in single living cancer cells by surface-enhanced Raman scattering (SERS) spectroscopy with the utilization of label-free Fe₃O₄@Ag core-satellite nanoparticles (NPs). The Fe₃O₄@Ag NPs can efficiently and selectively catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. Additionally, they exhibit excellent SERS activity that allows for in situ monitoring of intracellular H₂O₂ in living cells through establishing the correlation between the H₂O₂ level and the SERS intensity of the catalytic oxidation product of TMB. The H₂O₂ concentration is revealed through the SERS intensity of oxidized TMB with a good linear response in a wide range from 1 fM to 1 mM. Moreover, the intracellular H₂O₂ level in live cancer cells and imaging of the distribution of H₂O₂ inside single cells can be achieved by using such a label-free nanosensor based strategy. Our work demonstrates that the label-free Fe₃O₄@Ag NP-based SERS imaging and quantification strategy is a promising and powerful approach to assess intracellular H₂O₂ in living cells and allows us to monitor single-cell signaling molecules with nanoscale resolution.

New Insights of Charge Transfer at Metal/Semiconductor Interfaces for Hot-Electron Generation Studied by Surface-Enhanced Raman Spectroscopy

Plasmonic nanostructures with hot spots are very efficient in generating energetic (hot) electrons to realize light-driven chemical reactions. This effect primarily originates from high electric fields with nonuniform distribution in the hot-spot area. However, charge-transfer (CT) at plasmonic nanostructure interfaces and its effect on hot-electron generation have not been explored in detail. Here, a series of semiconductor/metal interfaces, with continuously adjustable energy-band structures, were constructed by the assembly of Cd_xZn_1-xS supports and Au nanoparticles (NPs) interconnected with p-aminothiophenol (PATP) molecules. The plasmon-mediated oxidation of PATP embedded in Cd_xZn_1-xS/PATP/45 nm-Au NP molecular junctions was systematically investigated using gap-mode-liked surface-enhanced Raman spectroscopy (SERS). Combining in situ SERS studies with energy-level analysis, interfacial CT was found to be a primary determinant of hot-electron-induced oxygen activation on large Au NP surfaces. This study provides a new perspective on the hot-electron generation mechanism to facilitate the rational design of efficient plasmonic photocatalysts.

Deprotonation from an OH on myo-Inositol Promoted by μ2-Bridges with Possible Regioselectivity/Chiral Selectivity

Single-crystal structures of myo-inositol complexes with erbium ([Er₂(C₆H₁₁O₆)₂(H₂O)₅Cl₂]Cl₂(H₂O)₄, denoted ErI hereafter) and strontium (Sr(C₆H₁₂O₆)₂(H₂O)₂Cl₂, denoted SrI hereafter) are described. In ErI, deprotonation occurs on an OH of myo-inositol, although the complex is synthesized in an acidic solution, and the pK_a values of all of the OHs in myo-inositol are larger than 12. The deprotonated OH is involved in a μ₂-bridge. The polarization from two Er³⁺ ions activates the chemically relatively inert OH and promotes deprotonation. In the stable conformation of myo-inositol, there are five equatorial OHs and one axial OH. The deprotonation occurs on the only axial OH, suggesting that the deprotonation possesses characteristics of regioselectivity/chiral selectivity. Two Er³⁺ ions in the μ₂-bridge are stabilized by five-membered rings formed by chelating Er³⁺ with an O-C-C-O moiety. As revealed by the X-ray crystallography study, the absolute values of the O-C-C-O torsion angles decrease from ∼60 to ∼45° upon chelating. Since the O-C-C-O moiety is within a six-membered ring, the variation of the torsion angle may exert distortion of the chair conformation. Quantum chemistry calculation results indicate that an axial OH flanked by two equatorial OHs (double ax-eq motif) is favorable for the formation of a μ₂-bridge, accounting for the selectivity. The double ax-eq motif may be used in a rational design of high-performance catalysts where deprotonation with high regioselectivity/chiral selectivity is carried out.

Progress of tip-enhanced Raman scattering for the last two decades and its challenges in very recent years

Tip-enhanced Raman scattering (TERS) has recently attracted remarkable attention as a novel nano-spectroscopy technique. TERS, which provides site-specific information, can be performed on any material surface regardless of morphology. Moreover, it can be applied in various environments, such as ambient air, ultrahigh vacuum (UHV), solutions, and electrochemical environments. This review reports on one hand progress of TERS for the last two decades, and on the other hand, its challenges in very recent years. Part of the progress of TERS starts with the prehistory and history of TERS, and then, the characteristics and advantages of TERS are described. Significant emphasis is put on the development of TERS instrumentation and equipment such as ultrahigh vacuum TERS, liquid TERS, electrochemical-TERS, and tip-preparations. Applications of TERS, particularly those with nanocarbons, biological materials, and surface and interface analysis, are mentioned in some detail. In the part on challenges, we focus on the very recent advances in TERS; progress in spatial resolution to the angstrom scale is the hottest topic. Recent TERS studies performed under UHV, for example chemical imaging at the angstrom scale and Raman detection of bond breaking and making of a chemisorbed up-standing single molecules at single-bond level, are reviewed. Of course, there is no clear border between the two parts. In the last part the perspective of TERS is discussed.

Novel Method for Extracting the Spectrum of a Supramolecular Complex via a Comprehensive Approach Involving Two-Dimensional Correlation Spectroscopy, Genetic Algorithm, and Grid Searching

A supramolecular complex may be formed by two solutes via a weak intermolecular interaction in a solution. The spectrum of the complex is often inundated by the spectra of the solutes that are not involved in the intermolecular interaction. Herein, a novel spectral analysis approach is proposed to retrieve the spectrum of the supramolecular complex. First, a two-dimensional (2D) asynchronous spectrum is constructed. Then, a genetic algorithm is used to obtain a heuristic spectrum of the supramolecular complex. The heuristic spectrum is a linear combination of the spectrum of the complex and the spectrum of a solute. The coefficients of the linear combination are then obtained, according to which the equilibrium constants are invariant among the sample solutions used to construct the 2D asynchronous spectrum. We have applied the approach to a supramolecular system formed by benzene and I₂. In the analysis, several binding models are evaluated, and a benzene molecule interacting with two iodine molecules via halogen bonding turns out to be the only possible model. Hence, the characteristic band of the benzene/I₂ supramolecular complex around 1819 cm^-1 in the Fourier transform infrared (FTIR) spectrum and the corresponding equilibrium constant are obtained. The above results indicate that the novel approach provides a chance to get new insight into various intermolecular interactions studied by spectroscopy.

A new approach to removing interference of moisture from FTIR spectrum

An approach is developed to remove the interference of moisture from FTIR spectra. The interference arises from two aspects: the fluctuation on the temperature of the HeNe laser and the fluctuation on the transient concentration of moisture in the light - path of an FTIR spectrometer. The temperature fluctuation on the HeNe laser produces a systematic spectral shift between single-beam sample and background spectra, which often makes spectral subtraction method invalid in removing the interference of moisture. Herein, the Carbo similarity metric (the C_AB value) is used to reflect the subtle spectral shift. A database of single-beam background spectra is established based on the concept of big-data and the pigeon-hole theory. The spectral shift is corrected by selecting suitable single-beam background spectra from the database to match with the given single-beam sample spectrum according to the C_AB value. The interference caused by the fluctuation of the transient concentration of moisture is removed using a comprehensive 2D-COS method. We apply the approach on two polymeric samples to retrieve high-quality spectra and reliable second derivative spectra without the interference of moisture. The present work provides a new opportunity of obtaining the reliable second derivative spectra in the spectral region masked by moisture.

Determination of the Influence of Various Factors on the Character of Surface Functionalization of Copper(I) and Copper(II) Oxide Nanosensors with Phenylboronic Acid Derivatives

In this work, we attempt to determine the influence of the oxidation state of copper [Cu(I) vs Cu(II)], the nature of the interface (solid/aqueous vs solid/air), the incubation time, and the structure of N-substituted phenylboronic acids (PBAs) functionalizing the surface of copper oxide nanostructures (NSs) on the mode of adsorption. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA) and its two analogues (2-PBA and bis{1-PBA}) and the copper oxide NSs were synthesized in a surfactant-/ion-free solution via a synthetic route that allows controlling the size and morphology of NSs. The NSs were characterized by scanning electron microscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, and X-ray diffraction, which confirmed the formation of spherical Cu2O nanoparticles (Cu2ONPs) with a size of 1.5 μm to 600 nm crystallized in a cubic cuprite structure and leaf-like CuO nanostructures (CuONSs) with dimensions of 80-180 nm in width and 400-700 nm in length and crystallized in a monoclinic structure. PBA analogues were deposited on the surface of the copper oxide NSs, and adsorption was investigated using surface-enhanced Raman spectroscopy (SERS). The changes in the orientation of the molecule relative to the substrate surface caused by the abovementioned factors were described, and the signal enhancement on the copper oxide NSs was determined. This is the first study using vibrational spectroscopy for these compounds.

An investigation of the effect of high-pressure on charge transfer in dye-sensitized solar cells based on surface-enhanced Raman spectroscopy

The interfacial charge transfer (CT) that plays an important role in enhancing the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) has not always been fully explored. Here, a TiO₂@N719@Ag DSSC system was constructed, and the CT processes have been monitored by surface-enhanced Raman scattering (SERS) spectra. Meanwhile, it is well known that as one of the most common external stimuli, high pressure can increase the free carrier density of TiO₂ NPs and cause the band gap to narrow. In the high pressure SERS experiment, we observed a significant enhancement of the N719 dye in the TiO₂@N719@Ag system up to 2.48 GPa, which is consistent with the variation trend of the charge transfer degree (ρ_CT). It is indicated that band gap changes will strongly affect the CT processes, further influence the SERS signal intensity (or ρ_CT), and thus increase the CT probability of DSSCs. Furthermore, the decoration of Ag NPs in the TiO₂@N719@Ag DSSC system can introduce localized surface plasmon resonance (LSPR), enhance the light trapping ability and offer additional CT pathways. Importantly, it is possible to improve the photoelectric conversion performance of DSSCs via the high pressure method and the introduction of Ag NPs. Finally, in order to observe the CT process of DSSCs more clearly, the models describing the CT mechanism have been proposed. SERS spectroscopy is expected to be a promising technique for the exploration of the interfacial CT behavior in DSSC devices, which may further broaden the thoughts of improvement of efficiency of the cells.

Solvent Effect on Assembling and Interactions in Solutions of Phenol: Infrared Spectroscopic and Density Functional Theory Study

This work provides new insight into assembling of phenol in various solvents and competition between different kinds of interactions. To examine both weak and strong interactions, we selected a series of non-aromatic and aromatic solvents. Infrared spectra were measured at low (0.05 M) and high (2 M) phenol content. In addition, we performed density functional theory calculations of the structures and harmonic vibrational spectra of 1:1 complexes of phenol with the solvents and the associates of phenol from dimer to tetramer. Based on these results, we divided the solvents into three groups. The first group consists of non-aromatic solvents weakly interacting with phenol. Depending on the concentration, molecules of phenol in these solvents remain non-bonded or self-associated. In diluted solutions of phenol in chlorinated non-aromatic solvents do not appear free OH groups, since they are involved in a weak OH···Cl interaction. It is of note that in diluted solutions of phenol in tetramethyl ethylene both the non-bonded and bonded OH coexists due to solvent-solvent interactions. The second group consists of aromatic solvents with methyl or chlorine substituents. At low concentration, the molecules of phenol are involved in the phenol-solvent OH···π interaction and the strength of these interactions depends on the solvent properties. At a higher phenol content an equilibrium exists between phenol-solvent OH···π and phenol-phenol OH···OH interactions. Finally, the third group includes the aromatic and non-aromatic solvents with highly polar group (C≡N). In these solvents, regardless of the concentration all molecules of phenol are involved in the solute-solvent OH···NC interaction. Comparison of the experimental and theoretical band parameters reveals that molecules of phenol in non-aromatic solvents prefer the cyclic associates, while in the aromatic solvents they tend to form the linear associates.

Development of an amino acid sequence-dependent analytical method for peptides using near-infrared spectroscopy

We aimed to develop an amino acid sequence-dependent analytical method using near-infrared (NIR) spectroscopy. The possibility for monitoring peptide synthesis was proved with very high accuracies.

Water-induced conformational changes in the powder and film of ε-poly(L)lysine studied by infrared and Raman spectroscopy

In this study, we have investigated the water absorption-induced structural changes and thermal behavior of ε-poly(L)lysine-hydrochloride (EPLHCl) in the powder and film samples using infrared (IR) and Raman spectroscopy. An X-ray diffraction measurement reveals that the crystal structure of ε-poly(L)lysine (EPL) is similar to that of the γ-crystal of nylon-6. The powder form of EPLHCl absorbs water from the air and solidifies into a film (18% water content). The film does not transform into the powder form with increasing temperature; it remains as a film, suggesting that the transformation from powder to film is irreversible. The IR spectra in the amide Ⅰ region of the powder and film are distinctly different, indicating that the secondary structure of EPLHCl changes upon water absorption. The position of the amide I band suggests that the powder form of EPLHCl has a β-sheet structure, while the film has two types of β-sheet structures. Raman spectra of EPLHCl in the region 1490-1440 cm^-1 indicate that the EPLHCl film has a trans amide structure, unlike its powder form. Hence, it is highly probable that the differences in the secondary structures of the EPLHCl powder and film originate due to the twisting of the amide group induced by water absorption.

Half-raspberry-like bimetallic nanoassembly: Interstitial dependent correlated surface plasmon resonances and surface-enhanced Raman spectroscopy

Correlated localized surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS) and localized electromagnetic (EM) field distributions of pure and modified gold (Au) nanoassemblies have been demonstrated. The Au nanoassemblies were decorated as half-raspberry-like nanostructures by silver (Ag) mists, and the characteristics of their SPR and SERS were observed at the same spatial position with and without decoration. The decoration of Au nanoassemblies was analyzed in-depth and confirmed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Multifunctional and lab-built microscopy was used to capture correlated SPR and SERS imaging and spectral measurements. Without decoration, strong SPR peaks and enhanced SERS signals were observed, whereas intense plasmon excitation deteriorated with a broadening and diminishing peak and the SERS enhancement dropped at least by 10 fold upon the modification. Preferential enhancement near the edge was observed in the correlated SPR and SERS measurements. The variations in localized SPR, subsequent SERS enhancement, and preferential confinement were speculated concerning localized EM near-field deformation. A typical tetramer with five interstitials was modeled and simulated by finite difference time domain (FDTD) analysis at different incident polarizations. The EM near-field distributions were extracted with and without decoration of constituent interstitials by Ag mists. Without the modification of participating interstitials, the EM near-field distributions were found confined, whereas additional EM near-field confinements were observed in the presence of Ag mists. Such EM near-field deformations due to the modification of constituent interstitials were supposed to broaden and deteriorate SPR characteristics of Au nanoassemblies as observed under this investigation.

Adoption of a new automated optical coherence tomography software to obtain a lipid plaque spread-out plot

Background

Near infrared spectroscopy – intravascular ultrasound (NIRS-IVUS) imaging can provide a fully automated estimation of lipid burden, providing a two-dimensional spread-out plot, the Lipid Core Burden Index (LCBI), which has been associated with higher incidence of cardiac events. Optical coherence tomography (OCT) can identify lipid component with high accuracy and it is therefore potentially capable of measuring its longitudinal extension in a dedicated two-dimensional LCBI spread-out plot.

Purpose

The present study has been designed to validate a novel automated approach to assess OCT images, able of providing a dedicated LCBI spread-out plot plus other features of plaque vulnerability.

Methods

We compared the results obtained with a novel automated OCT alghorithm, developed utilising a convolutional neural network, with those obtained with conventional (manual) OCT and with NIRS-IVUS in a consecutive series of 40 patients with coronary artery disease. We tested and validated our new OCT algorithm to calculate the lipid core longitudinal extension in a dedicated two-dimensional LCBI spread-out plot. In each coronary plaque, the following measurements were obtained with NIRS-IVUS: 1) minimum lumen area (MLA), 2) vessel area at MLA site, 3) plaque burden (%) at MLA site, 4) NIRS-defined lipid pool arch and 5) maximum LCBI measurement within a 4 mm length. The following OCT features were obtained: 1) the MLA cross section, 2) the minimum fibrous cap thickness (FCT) in presence of lipid components and measured as the average of three measurements obtained in the same cross-section and 3) maximum LCBI within a 4 mm length.

Results

Three lesions groups were identified according to the studied lesions: 1) culprit lesions in patients with acute coronary syndrome (ACS, n=16), 2) non-culprit lesions in patients with ACS (n=12) and 3) lesions in patients with stable angina (n=12). OCT conventional assessment showed for the culprit ACS plaques a trend for a larger lipid arc and a significant thinner FCT (p=0.028). Consistently, NIRS-IVUS showed for culprit ACS plaques a more complex anatomy. A strong trend for increased maximum LPBI in 4mm segments was found in the culprit ACS group, regardless of the adopted imaging modality, either NIRS-IVUS or automated OCT (p=0.184 and p=0.066, respectively, figure 1). A fair correlation was obtained for the maximum 4 mm LCBI measured by NIRS-IVUS and automated OCT (r=0.75). The sensitivity and specificity of automated OCT to detect significant LCBI, applying a validated 400 cut off were 90.5 and 84.2 respectively.

Conclusions

We developed an automated approach, comparable to NIRS, to assess OCT images that can provide a dedicated lipid plaque spread-out plot to address plaque vulnerability. The automated OCT software can promote and improve OCT clinical applications for the identification of patients at risk of hard events.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): CLI - Centro Lotta all'Infarto Spread-out plot by IVUS-NIRS and OCT

Far-Ultraviolet Spectroscopy and Quantum Chemical Calculation Studies of the Conformational Dependence on the Electronic Structure and Transitions of Cyclohexane, Methyl and Dimethyl Cyclohexane, and Decalin; Effects of Axial Substitutions on the Electronic Transitions

Far-ultraviolet (FUV) spectra were measured for cyclohexane, methyl cyclohexane, six isomers of dimethyl cyclohexane, and cis- and trans-decalin. Attenuated total reflection-FUV (ATR-FUV) spectroscopy, which we originally proposed, provides systematic information about the excitation states of saturated organic molecules and the hyperconjugation of σ bonds. The FUV spectra of cyclohexane and methyl cyclohexane in neat liquids showed a band with central wavelengths near 155 and 162 nm. The simulation spectrum of cyclohexane calculated by time-dependent density-functional theory (TD-DFT) (CAM-B3LYP/aug-cc-pVTZ) gives two bands at 146 and 152 nm owing to the transition from HOMO-2 to Rydberg 3pz (Tb) and those from HOMO and HOMO-1 to Rydberg 3px/3py (Ta), respectively. The simulation spectrum of methyl cyclohexane with the equatorial substituent has peaks at approximately the same positions as cyclohexane. The calculated molar absorption coefficient is larger than that of cyclohexane, estimating the observed FUV spectra very well. The FUV spectra of dimethyl cyclohexane with two methyl substituents at the equatorial positions (trans-1,2-, cis-1,3-, and trans-1,4-) and trans-decalin had similar features to those of cyclohexane and methylcyclohexane. The TD-DFT calculations revealed that the shoulders at the shorter- and longer-wavelength sides of the band center of dimethyl cyclohexane (with methyl substituents at equatorial positions) and trans-decalin are assigned to Tb and Ta, respectively. In the case of dimethyl cyclohexane with one methyl substituent in the axial position (cis-1,2-, trans-1,3-, and cis-1,4-) and cis-decalin, the band caused by Tb decreased compared to those of the other compounds. The decrease in intensity and the longer-wavelength shift of the Tb band for dimethyl cyclohexane (with one methyl group at the axial position) and cis-decalin revealed that the band on the longer-wavelength side was assigned to the overlap band of Ta and Tb. The reason for such a large spectral alternation for the axial substitution may be the increase in the orbital energy of HOMO-2, which has its electron density concentrated at the axial C-H bond. Regarding the effect of the hyperconjugation of C-C and C-H σ orbitals, the second perturbation energies of the interaction between C_α-H_ax and C_β-H_ax were estimated for molecules by natural bond orbital (NBO) analysis. There is a correlation between the orbital energies of HOMO-2 and the changes in vicinal interaction by axial substitution.