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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 253: 119549, 2021 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-33621936

RESUMO

Far-ultraviolet (FUV) spectroscopy in the region of 140-200 nm of condensed-phase has received keen interest as a new electronic spectroscopy. The introduction of the attenuated total reflection (ATR) technique to the FUV region has opened a new avenue for FUV spectroscopy of liquids and solids. ATR-FUV spectroscopy enables the study of electronic structures and transitions of most types of molecules. It also holds great promise for a variety of applications, i.e., from the application to basic sciences to practical applications. In this review, the characteristics and advantages of ATR-FUV spectroscopy in the condensed phase are described first; then, a brief historical overview is provided. Next, the ATR-FUV spectroscopy instrumentation is outlined. After these introductory parts, a variety of AFT-FUV spectroscopy applications are introduced, starting from applications to investigations of electronic structure and transitions of alkanes, graphenes, and polymers. Then, time-resolved ATR-FUV spectroscopy is discussed. The applications to materials research, such as the research on inorganic semiconductors and ionic liquids, follow. In the last part, the FUV spectroscopy perspective is emphasized.

3.
Spectrochim Acta A Mol Biomol Spectrosc ; 251: 119427, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33461134

RESUMO

Terbium acetylsalicylate has been prepared, and the ethanol solution of the complex exhibits strong luminescence under the excitation of ultraviolet radiation. When a small amount of bilirubin solution is introduced into the solution containing a high concentration of terbium acetylsalicylate, a remarkable diminution of the luminescence of the terbium complex was observed. Investigations on the behavior and life-time of luminescence indicate that the quenching is not caused by forming a stable non-luminescent product via a reaction between terbium acetylsalicylate and bilirubin. A π-π interaction between the chromophore of bilirubin and the aromatic moiety of ligand was revealed via the pattern of cross peaks in the 2D asynchronous spectrum generated using the DAOSD (double asynchronous orthogonal sample design) approach. Such an interaction paves a route for energy transfer in the quenching process. The combination of a high concentration of the terbium complex and a long life-time of luminescence in the lanthanide complex/bilirubin system forms a special scenario: a bilirubin molecule by diffusion may visit and deactivate dozens of excited terbium complexes within the half-life period of the lanthanide complex. This is why a small amount of bilirubin can bring about the significant reduction of luminescence on the solution containing a high concentration of the terbium complex.

4.
Biosens Bioelectron ; 171: 112748, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33113381

RESUMO

Protein phosphorylation, a post-translational modification of proteins, is of vital importance in biological regulation. Highly sensitive and site-specific identification of phosphorylated proteins is a key requirement for unraveling crucial signal transduction pathways relevant to cancers and neurodegenerative disorders. Traditional detection methods, however, suffer from relying on antibodies, labels or fragmentation prior to analysis. Here, an antibody- and label-free in situ approach to fingerprint protein phosphorylation was developed based on intrinsic Raman vibrational information of phosphorylated tyrosine, serine, threonine, or histidine residues. Combining surface-enhanced Raman scattering (SERS) spectroscopy and an immobilized-metal affinity strategy, this method is ultrasensitive to discriminate a single-site phosphorylated S396 in a Tau410 protein, an important biomarker in Alzheimer's disease. The binding feasibility of phosphorylated proteins to the modified SERS-active materials is further evidenced by molecular dynamics simulations. This proof-of-concept study paves a new way for the evaluation of site-specific and intact protein phosphorylation in both fundamental mechanical investigation and clinical applications.

5.
Anal Chem ; 93(5): 2758-2766, 2021 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-33356160

RESUMO

Using near-infrared (NIR) spectroscopy, we aimed to develop a method of monitoring the increasing number of amide bonds with the elongation of the chain length of peptides. Because peptide synthesis can be monitored by evaluating the increasing number of amide bonds with dehydration occurring between amino acids, polyglycine, which has the simplest structure among polyamino acids, was studied, and the key bands whose absorption intensities increased with the elongation of the chain length, such as the bands attributed to glycine, diglycine, triglycine, and tetraglycine, were searched. The bands due to the combinations of the amide A and amide II/III modes in the region of 5000-4500 cm-1 were revealed to be good candidates for key bands, their second derivative intensities increased as the number of amide bonds increased, regardless of pH, solvent species, and the presence of protecting groups. The number of amide bonds was evaluated by a partial least square regression using the abovementioned combination bands, and a calibration model with a high determination coefficient (≥0.99) was constructed. These results not only have demonstrated the usefulness of NIR spectroscopy as a process analytical technology tool for the process of synthesizing the peptide in a microflow reactor but also have provided basic knowledge for analyzing amide bonds in the NIR spectra of proteins, polyamino acids, polypeptides, and polyamides.

6.
J Hazard Mater ; 405: 124642, 2020 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-33301972

RESUMO

Total removal of organic mercury in industrial wastewater is a crucially important task facing environmental pollution in the current world. Herein, we demonstrate the fabrication of Au-NiFe layered double hydroxide (LDH)/rGO nanocomposite as not only an efficient nanozyme with oxidase-like activity but also an efficient surface-enhanced Raman spectroscopy (SERS) substrate to determine organic mercury, with the minimum detection concentration as low as 1 × 10-8 M. According to the binding energy of X-Ray photoelectron spectrometer (XPS) and the free radicals of electron paramagnetic resonance (EPR) spectra, the mechanism of catalytic enhanced degradation is the production of Au-amalgam on Au surface, accelerating the electron transfer and the generation of O2•- radicals from oxygen molecules and •CH3 radicals from the methyl group in MeHg to participate the oxidase-like reaction. Furthermore, the Au-NiFe LDH/rGO nanocomposite is able to degrade and remove 99.9% of organic mercury in two hours without the secondary pollution by Hg2+. In addition, the material can be used for the multiple degradation-regeneration cycles in actual applications, which is significant in terms of the environmental and economic point of view. This work may open a new horizon for both highly sensitive detection and thorough degradation of organic mercury in environmental science and technology.

7.
Appl Spectrosc ; : 3702820971714, 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33103490

RESUMO

Previously, we demonstrated that the intensities of cross-peaks in a two-dimensional asynchronous spectrum could be enhanced using sequence change of the corresponding one-dimensional spectra. This unusual approach becomes useful when the determination of the sequential order of physicochemical events is not essential. However, it was not known whether the level of noise in the two-dimensional asynchronous spectrum was also escalated as the sequence of one-dimensional spectra changed. We first investigated the noise behavior in a two-dimensional asynchronous spectrum upon changing the sequence of the corresponding one-dimensional spectra on a model system. In the model system, bilinear data from a chromatographic-spectroscopic experiment on a mixture containing two components were analyzed using a two-dimensional asynchronous spectrum. The computer simulation results confirm that the cross-peak intensities in the resultant a two-dimensional asynchronous spectrum were indeed enhanced by more than 100 times as the sequence of one-dimensional spectra changed, whereas the fluctuation level of noise, reflected by the standard deviation of the value of a two-dimensional asynchronous spectrum at a given point, was almost invariant. Further analysis on the model system demonstrated that the special mathematical property of the Hilbert-Noda matrix (the modules of all column vectors of the Hilbert-Noda matrix being a near constant) accounts for the moderate variation of the noise level during the changes of the sequence of one-dimensional spectra. Next, a realistic example from a thermogravimetry-Fourier transform infrared spectroscopy experiment with added artificial noise in seven one-dimensional spectra was studied. As we altered the sequence of the seven FT-IR spectra, the variation of the cross-peak intensities covered four orders of magnitude in the two-dimensional asynchronous spectra. In contrast, the fluctuation of noise in the two-dimensional asynchronous spectra was within two times. The above results clearly demonstrate that a change in the sequence of one-dimensional spectra is an effective way to improve the signal-to-noise level of the two-dimensional asynchronous spectra.

8.
Anal Chim Acta ; 1134: 34-40, 2020 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-33059864

RESUMO

Urinary 5-hydroxyindole-3-acetic acid (5-HIAA) is a marker for diagnosis of patients with carcinoid tumors. In clinical practice, a simple colorimetric assay has widely been utilized for urinary 5-HIAA via its reaction with 1-nitroso-2-naphthol (NNa) in nitrous acid medium. However, this colorimetric assay has been criticized for lack of specificity. Herein, we proposed a novel SERS-based method for selective detection of urinary 5-HIAA by the use of a modified nitrosonaphthol reaction, in which hydrochloric acid is substituted for nitric acid to control the reaction conditions. This slight modification is crucial to be able to detect the cationic products in the acidic reaction mixture, because the chloride-aggregated Ag colloids not only create enormous hot spots for SERS enhancement, but also improve the chemical stability of nanostructured Ag substrates in acidic environment. Under optimized conditions, the present method can detect 5-HIAA within 12 min at concentrations as low as 1.2 ng/mL, which is 1000 times lower than that of conventional colorimetric method. And more importantly, the present method exhibits specific response toward 5-HIAA against other metabolites with similar structures in the urine. The relative standard deviation (RSD) of the present method is less than 5%, suggesting the acceptable reproducibility. The recoveries ranging from 89.6% to 106.3% were obtained for spiked human urine samples with RSD of 3.7-4.9%. Furthermore, several healthy person's urine samples were also analyzed using the present method, and experimental results are in compliance with the levels recorded in a healthy population. On the basis of these results we can conclude that the present SERS-based method can provide a valuable alternative to conventional colorimetric assay for clinical diagnosis, evaluating prognosis, and monitoring of treatment in carcinoid tumors.

9.
Sci Rep ; 10(1): 16741, 2020 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-33028868

RESUMO

It is recently suggested that amyloid polymorphism, i.e., structural diversity of amyloid fibrils, has a deep relationship with pathology. However, its prompt recognition is almost halted due to insufficiency of analytical methods for detecting polymorphism of amyloid fibrils sensitively and quickly. Here, we propose that iodine staining, a historically known reaction that was firstly found by Virchow, can be used as a method for distinguishing amyloid polymorphs. When insulin fibrils were prepared and iodine-stained, they exhibited different colors depending on polymorphs. Each of the colors was inherited to daughter fibrils by seeding reactions. The colors were fundamentally represented as a sum of three absorption bands in visible region between 400 and 750 nm, and the bands showed different titration curves against iodine, suggesting that there are three specific iodine binding sites. The analysis of resonance Raman spectra and polarization microscope suggested that several polyiodide ions composed of I3- and/or I5- were formed on the grooves or the edges of ß-sheets. It was concluded that the polyiodide species and conformations formed are sensitive to surface structure of amyloid fibrils, and the resultant differences in color will be useful for detecting polymorphism in a wide range of diagnostic samples.

10.
Phys Chem Chem Phys ; 22(38): 21768-21775, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-32960190

RESUMO

The electronic states of N-butyl-N-methylpyrrolidinium dicyanamide ([BMP][DCA]), a solvated ionic liquid, around Li+ were investigated using attenuated total reflectance far-ultraviolet and deep-ultraviolet (ATR-FUV-DUV) spectroscopy. The absorption bands ascribed to the [DCA]- were blue-shifted as the Li+ concentration increased, and the origin of the shift was explained by the energetic destabilization of the final (excited) molecular orbital using time-dependent density functional theory (TD-DFT) calculations. Using the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm, the obtained spectra were decomposed into two types of [DCA]- at electronic state level, which were categorised as pure [BMP][DCA] and [DCA]- affected by Li+. Our results revealed that the number of [DCA]- with electronic states affected by a Li+, which was termed the electronic coordination number, was ∼5. This value was different from the coordination number within the first solvation layer, which was ∼4. Combining the TD-DFT with molecular dynamics simulations, we demonstrated that one [DCA]- outside the first solvation layer had a different electronic state from that of pure [BMP][DCA]. This is the first successful study that combines ATR-FUV-DUV spectroscopy with MCR-ALS calculations to build a solvation model that describes the electronic states.

11.
Spectrochim Acta A Mol Biomol Spectrosc ; 243: 118789, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32799191

RESUMO

Systematic Absence of Cross Peaks (SACPs) in a two-dimensional (2D) asynchronous spectrum, a sensitive indicator of the signal purity, is very important in analyzing bilinear data. However, identification of SACPs in practice remains a challenge because of noise in the corresponding 2D asynchronous spectrum. We firstly show that SACP can be identified via a statistical test using a large amount of 2D asynchronous spectra. To meet the practical demand that SACPs must be identified based on a single 2D asynchronous spectrum in many cases, we use a 2D quotient spectrum (Q (x, y)) as an effective auxiliary tool to recognize SACPs. The expectation of Q(x, y) is zero when (x, y) is within SACP or background regions in the corresponding 2D asynchronous spectrum. When (x, y) is in a cross-peak region, the expectation of the absolute value of Q(x, y) is a constant regardless of whether the cross-peak in a 2D asynchronous spectrum is strong or weak. Thus, a unified threshold can be set up to differentiate the SACP region from cross-peak region via the auxiliary 2D quotient spectrum. We have applied this approach on two real-world examples and satisfactory results have been obtained. This result demonstrates that the statistical test with a 2D quotient spectrum is applicable in real-world systems.

12.
Angew Chem Int Ed Engl ; 59(43): 19079-19086, 2020 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-32725876

RESUMO

A versatile and robust chiral discrimination strategy for small aromatic compounds is of significant importance in multidisciplinary fields. However, most current methods lack either the sufficient sensitivity for recognizing the chirality of the target molecules or their molecular specificity information. We have developed a versatile and chiral-label-free surface-enhanced Raman scattering (SERS)-based chiral discrimination sensing system for small aromatic molecules, where the molecular structural specificity and enantioselectivity can be given synchronously in a single SERS spectrum. More than 10 types of chiral aromatic molecules were successfully identified by using this system. This work has enormous potential for recognizing chiral products effectively in sophisticated systems, especially in the fields of chiral synthesis and chiral catalysis.

13.
Appl Spectrosc ; 74(11): 1384-1390, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32627577

RESUMO

Interactions between epitaxial graphene grown on Si- and C-faces were investigated using Raman imaging and tip-enhanced Raman scattering (TERS). In the TERS spectrum, which has a spatial resolution exceeding the diffraction limit, a D band was observed not from graphene surface, but from the edges of the epitaxial graphene ribbons without a buffer layer, which interacts with SiC on the Si-face. In contrast, for a graphene micro-island on the C-face, the D band disappeared even on the edges where the C atoms were arranged in armchair configurations. The disappearance of the edge chirality via combination between the C atoms and SiC on the C-face is responsible for this phenomenon. The TERS signals from the C-face were weaker than those from the Si-face without the buffer layer. On the Si-face with a buffer layer, the graphene TERS signal was hardly observed. TERS enhancement was suppressed by interactions on the edges or by the buffer layer between the SiC and graphene on the C- or Si-face, respectively.

14.
Anal Chem ; 92(17): 11763-11770, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32697077

RESUMO

Surface-enhanced Raman scattering (SERS) is a supersensitive technique for monitoring catalytic reactions. However, building a SERS-kinetics model to investigate catalytic efficiency on the surface or interface of the catalyst remains a great challenge. In the present study, we successfully obtained an excellent semiconducting SERS substrate, reduced MnCo2O4 (R-MnCo2O4) nanotubes, whose favorable SERS sensitivity is mainly related to the promoted interfacial charge transfer caused by the introduction of oxygen vacancies as well as the electromagnetic enhancement effect. Furthermore, the R-MnCo2O4 nanotubes showed a favorable oxidase-like activity toward oxidation with the aid of molecular oxygen. It was also showed the oxidase-like catalytic process could be monitored using the SERS technique. A new SERS-kinetics model to monitor the catalytic efficiency of the oxidase-like reaction was developed, and the results demonstrate that the Vm values measured by the SERS-kinetics method are close to that obtained by the UV-vis approach, while the Km values measured by the SERS-kinetics method are much lower, demonstrating the better affinity between the enzyme and the substrate from SERS results and further confirming the high sensitivity of the SERS-kinetics approach and the actual enzyme-like reaction on the surface of nanozymes, which provides guidance in understanding the kinetics process and catalytic mechanism of natural enzymatic and other artificial enzymatic reactions. This work demonstrated the improved SERS sensitivity of defective semiconductors for the application of enzyme mimicking, providing a new frontier to construct highly sensitive biosensors.

15.
Angew Chem Int Ed Engl ; 59(34): 14564-14569, 2020 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-32492238

RESUMO

Discrimination between enantiomers is achieved by tip-enhanced Raman scattering (TERS) using a silver tip that is chemically modified by an achiral para-mercaptopyridine (pMPY) probe molecule. Differences in the relative intensities of the pMPY spectra were monitored for three pairs of enantiomers containing hydroxy (-OH) and/or amino (-NH2 ) groups. The N: or N+ -H functionality of the pMPY-modified tip participates in hydrogen-bond interactions with a particular molecular orientation of each chiral isomer. The asymmetric arrangement of silver atoms at the apex of the tip induces an asymmetric electric field, which causes the tip to become a chiral center. Differences in the charge-transfer (CT) states of the metal-achiral probe system in conjunction with the asymmetric electric field produce different enhancements in the Raman signals of the two enantiomers. The near-field effect of the asymmetric electric field, which depends on the number of analyte functional groups capable of hydrogen-bond formation, improves the degree of discrimination.

16.
Phys Chem Chem Phys ; 22(23): 13017-13029, 2020 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-32478350

RESUMO

Previous measurements of fundamental, first-, second- and third overtones of the OH-stretching vibration of phenol and 2,6-difluoro-phenol by use of visible (Vis), near-infrared (NIR) and infrared (IR) spectroscopy revealed an oscillating pattern in the intensity quotient between the two kinds of solvents, carbon tetrachloride and n-hexane, upon increase of the vibrational quantum number, which could not be reproduced utilizing quantum mechanical calculations in implicit solvation. In the present study this phenomenon was successfully explained for the first time, employing an explicit consideration of solute-solvent interactions in combination with modern grid-based methods to solve the time-independent Schrödinger equation. The capabilities of this framework of (i) not requiring any assumptions on the form of the resulting wave function, (ii) focusing the description on the vibrational mode of interest and (iii) taking solute-solvent interactions explicitly into account are a particularly lucid example of the advantages in applying state-of-the-art approaches in investigations of challenging vibrational quantum problems. The property of grid-based methods being directly applied onto any given potential energy grid together with point (i) enable to analyse the impact of mechanical- and electrical anharmonicity independently. Especially the detailed investigation of the latter contribution when moving from a harmonic to an anharmonic potential in conjunction with the explicit consideration of solvent effects at the example of an actual chemical system (i.e. not discussing these effects employing mere model potentials) demonstrate the manifold benefit achieved using the applied DFT/Numerov strategy.

17.
Sci Rep ; 10(1): 9938, 2020 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-32555405

RESUMO

In this study, surface plasmon resonance (SPR) wavelength shifts due to molecular electronic absorptions in the far-ultraviolet (FUV, < 200 nm) and deep-ultraviolet (DUV, < 300 nm) regions were investigated by attenuated total reflectance (ATR) spectroscopy. Due to the strong absorption in the DUV region, N,N-dimethylformamide (DMF) significantly increased the SPR wavelength shift of Al film. On the other hand, no such shift enhancement was observed in the visible region for Au film because DMF does not have absorbance compared to non-absorbing materials such as water and alcohols. The enhanced SPR wavelength shift, caused by the overlap between SPR and molecular resonance wavelengths in FUV-DUV region, is expected to result in high sensitivity for resonant materials.

18.
Anal Chem ; 92(12): 8133-8141, 2020 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-32407102

RESUMO

We explored the influence of embryonic bioactivity on the water structure using near-infrared (NIR) spectroscopy and imaging. Four groups of Japanese medaka fish (Oryzias latipes) eggs were studied: (a) one group of eggs was activated by fertilization, and (b-d) three groups of eggs were not activated because embryogenesis was stopped or not started by (b) culturing under cold temperature, (c) instant freezing, or (d) lack of fertilization. The yolks of the activated eggs contained higher proportions of weakly hydrogen bonded water than those of nonactivated eggs. A possible factor responsible for the significant changes in the water structure was revealed to be a protein secondary structural change from an α-helix to a ß-sheet in the activated eggs. NIR images of the activated eggs successfully visualized the water structural variation in the yolk with a higher proportion of weak hydrogen bonds due to the activation of embryonic development. The embryogenic activity could be assessed through the water hydrogen bond network, which is affected by newly generated proteins with different secondary structures.

19.
Biophys J ; 118(12): 2997-3007, 2020 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-32428440

RESUMO

We aimed to investigate insulin amyloid fibril polymorphism caused by salt effects and heating temperature and to visualize the structural differences of the polymorphisms in situ using Raman imaging without labeling. The time course monitoring for amyloid formation was carried out in an acidic condition without any salts and with two species of salts (NaCl and Na2SO4) by heating at 60, 70, 80, and 90°C. The intensity ratio of two Raman bands at 1672 and 1657 cm-1 due to antiparallel ß-sheet and α-helix structures, respectively, was revealed to be an indicator of amyloid fibril formation, and the relative proportion of the ß-sheet structure was higher in the case with salts, especially at a higher temperature with Na2SO4. In conjunction with the secondary structural changes of proteins, the S-S stretching vibrational mode of a disulfide bond (∼514 cm-1) and the ratio of the tyrosine doublet I850/I826 were also found to be markers distinguishing polymorphisms of insulin amyloid fibrils by principal component analysis. Especially, amyloid fibrils with Na2SO4 media formed the gauche-gauche-gauche conformation of disulfide bond at a higher rate, but without any salts, the gauche-gauche-gauche conformation was partially transformed into the gauche-gauche-trans conformation at higher temperatures. The different environments of the hydroxyl groups of the tyrosine residue were assumed to be caused by fibril polymorphism. Raman imaging using these marker bands also successfully visualized the two- and three- dimensional structural differences of amyloid polymorphisms. These results demonstrate the potential of Raman imaging as a diagnostic tool for polymorphisms in tissues of amyloid-related diseases.

20.
J Phys Chem B ; 124(20): 4089-4096, 2020 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-32343576

RESUMO

The molecular mechanism of blue color formation in an iodine-starch reaction is studied by employing the iodine-α-cyclodextrin (α-CD) complex as a practical model system that resembles the structural properties of the blue amylose-iodine complex. To this end, we construct, using the quantum chemistry method, a molecular model of the complex (I5-/Li+/2α-CD) that consists of one I5-, two molecules of α-CD, and a lithium cation, and this model is employed as a basic unit in constructing the structural models of polyiodide ions (I5-)n. The initial structure in the geometry optimization is adopted from the α-CD-iodine complex structure obtained from the X-ray crystallography study. The structural models of (I5-)n are built by adding the basic unit n times along the crystal axis and by optimizing the structure using quantum mechanics/molecular mechanics (QM (iodine)/MM (α-CD)) calculations. The electronic absorption spectra of the resulting model structures are calculated by time-dependent density functional theory (TD-DFT). We find that I5- acts as a basic unit of coloration in the visible region. The visible color originates from the electronic transition within the I5- molecule, and any charge transfer between the I5- ion and either of α-CD or a coexisting counter cation is not involved. We also reveal that the electronic transitions of (I5-)n are delocalized, which accounts for the well-known observation that the color of the iodine-starch reaction becomes bluish with an increase in the chain length of amylose. Furthermore, the preresonance Raman spectra calculated from the model suggest that the vibrational motions are localized in the I5- subunit dominantly. A comparison between an experimental absorption spectrum feature of the α-CD-iodine complex and the calculated ones of (I5-)n ions with various n values suggests that (I5-)4 polyiodide ions tend to be populated dominantly in the α-CD-iodine complex under aqueous conditions.

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