Raman Optical Activity

Barron, Laurence D.

doi:10.1007/978-94-015-7644-4_9

Cited by 31 publications

(4 citation statements)

References 51 publications

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“…The long-sought goal of sampling chiroptical properties of more transitions than are accessible in the UV, especially those that are spectrally resolved and reflect ground state structures, prompted the development of vibrational CD (VCD) and Raman optical activity (ROA) in the 1970s. − The key element in successfully building VCD instrumentation was the then newly available, high sensitivity, relatively fast diode mid-IR detectors, and improved quality IR polarization optics. With extension to FTIR based VCD methods as developed by Nafie and co-workers and the subsequent commercialization of FT-VCD instrumentation, VCD has become widespread and is now most widely used for determination of absolute configuration of small to midsized organic molecules. ,− Such studies depend on interpreting experimental spectra in terms of conformation and configuration with density functional theory (DFT) level spectral simulations and are particularly valuable in pharmacological and natural product applications. − Since VCD is a vibrational spectroscopy with inherently more resolved transitions, it does not have spectral interference problems from aromatics, disulfides, or most buffers.…”

Section: Introductionmentioning

confidence: 99%

Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques

2020

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Peptides and proteins are naturally chiral molecular systems so that sensing their structure and conformation with chirality-based spectral methods is an obvious and long-used diagnostic application. Extending chiroptical techniques to measurement of vibrational transitions, in the form of vibrational circular dichroism (VCD) and Raman optical activity (ROA), expands the number and types of excitations available that might provide structural insight and can provide an alternate and, in some cases, a more distinctive conformational probe. Since the dominant repeating structural element in peptides is the locally achiral amide group, VCD senses the polymeric structure through amide coupling, which is directly dependent on secondary structure. Determination of the type and relative contribution of these structural components through empirical correlation with spectral character has been the main application of VCD for peptides and proteins, although this is now reinforced by extensive theoretical modeling. Monitoring structural and conformational change induced by environmental perturbations provides another important application. More recently, VCD has been used to detect morphological variations in fibril states of aggregated peptides and proteins. ROA has parallel secondary structural sensitivities, with more applications for proteins than peptides, and has more sensitivity to local configuration and side chains. This review covers the range of peptide studies done with VCD and extends them to compare with example protein and ROA applications.

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Section: Introductionmentioning

confidence: 99%

Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques

2020

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“…As a result, based on the importance of chirality in chemical and pharmaceutical sciences, detection and characterization of chiral particles (materials) are fundamentally critical issues. In order to resolve these issues, spectroscopy techniques based on optical rotation (OR), circular dichroism (CD), and Raman optical activity (ROA) have been proposed [3][4][5][6]. In these chiroptical techniques, the scattered (refracted or absorbed) light from the sample is measured to detect the chirality.…”

Section: Introductionmentioning

confidence: 99%

Enantio-specific Detection of Chirality at Nanoscale Using Photo-induced Force

Kamandi

Albooyeh

Rajaei

et al. 2018

Conference on Lasers and Electro-Optics

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We propose a novel high resolution microscopy technique for enantio-specific detection of chiral samples down to sub-100 nm size, based on force measurement. We delve into the differential photo-induced optical force F  exerted on an achiral probe in the vicinity of a chiral sample, when left and right circularly polarized beams separately excite the sample-probe interactive system. We analytically prove that F  is entangled with the enantiomer type of the sample enabling enantio-specific detection of chiral inclusions. Moreover, we demonstrate that F  is linearly dependent on both the chiral response of the sample and the electric response of the tip and is inversely related to the quartic power of probe-sample distance. We provide physical insight into the transfer of optical activity from the chiral sample to the achiral tip based on a rigorous analytical approach. We support our theoretical achievements by several numerical examples, highlighting the potential application of the derived analytic properties. Lastly, we demonstrate the sensitivity of our method to enantiospecify nanoscale chiral samples with chirality parameter in the order of 0.01, and discuss how this could be further improved.

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“…Indeed, the optical activity of chiral structures is a key parameter in molecular identification techniques to recognize the type of molecule or to determine its structure thanks to the discriminatory behavior of chiral molecules in interaction with the incident light possessing a distinct sense of polarization. , For instance, for a protein, determining the structure refers to resolving its four levels of complexity, i.e., primary, secondary, tertiary, and quaternary, which defines not only the sequence of amino acids but also reveals the three-dimensional arrangement of atoms in that protein . This information is of supreme importance in modifying and utilizing proteins for new purposes such as creating protein-based antibody drug conjugates for cancer treatment or modifying the proteins in bread. − To determine the structure of chiral samples such as protein, noninvasive spectroscopic techniques based on optical rotation (OR), circular dichroism (CD), and Raman optical activity (ROA) have been proposed and vastly studied. − In these methods, owing to the optical activity of chiral structures, the difference between the absorbed left-hand and right-hand circularly polarized (CP) light is measured, and not only the chirality but also some important information about the structure of a chiral sample is obtained. − Specifically using CD, one can approximate the secondary structure of a protein. However, the main limitations of this method are as follows: (i) it is unable to provide high-resolution structural details and (ii) it demands a considerable amount of material for detection.…”

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confidence: 99%

Unscrambling Structured Chirality with Structured Light at the Nanoscale Using Photoinduced Force

et al. 2018

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We introduce a microscopy technique that facilitates the prediction of spatial features of chirality of nanoscale samples by exploiting the photo-induced optical force exerted on an achiral tip in the vicinity of the test specimen. The tip-sample interactive system is illuminated by structured light to probe both the transverse and longitudinal (with respect to the beam propagation direction) components of the sample's magnetoelectric polarizability as the manifestation of its sense of handedness, i.e., chirality. We specifically prove that although circularly polarized waves are adequate to detect the transverse polarizability components of the sample, they are unable to probe the longitudinal component. To overcome this inadequacy and probe the longitudinal chirality, we propose a judiciously engineered combination of radially and azimuthally polarized beams, as optical vortices possessing pure longitudinal electric and magnetic field components along their vortex axis, respectively. The proposed technique may benefit branches of science like stereochemistry, biomedicine, physical and material science, and pharmaceutics. 1) LOCAL FIELDS AT THE TIP-APEX AND SAMPLE LOCATION, EXCITED BY AN ARPBWe prove that under ARPB excitation (a superposition of two coaxial beams: an APB and an RPB with proper phase shift  ) the local fields at the tip-apex and sample locations (both on the ARPB axis, see Fig. 1 of the paper) lack transverse components and we determine the longitudinal field components that include the near-field interaction. We consider the schematic of the problem in Fig. 1 of the manuscript and assume that the tip-apex and chiral sample are located at t z and s z , respectively, at a distance d from each other.

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Raman Optical Activity

Cited by 31 publications

References 51 publications

Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques

Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques

Enantio-specific Detection of Chirality at Nanoscale Using Photo-induced Force

Unscrambling Structured Chirality with Structured Light at the Nanoscale Using Photoinduced Force

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