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Absorption spectra of Muler cell intermediate filaments: experimental results and theoretical models

2020-09-05Journal article Restricted access
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dc.contributor.authorKhmelinskii, Igor
dc.contributor.authorMakarov, Vladimir
dc.date.accessioned2021-06-24T11:35:17Z
dc.date.available2021-06-24T11:35:17Z
dc.date.issued2020-09-05
dc.description.abstractExperimental spectra of Muller cell (MC) intermediate filaments (IFs) isolated from porcine retina are reported in this work. The absorption spectra recorded at different MC IF concentrations were used to estimate their absorption cross-sections at different wavelengths. The average absorption cross-section of a single MC IF was ca. (0.97...2.01) x 10(-1) cm(2) in the 650-445 nm spectral range. To interpret these experimental absorption spectra, we made ab initio calculations of the optical spectra of a-helix polypeptides, and also used a simplified theoretical approach that modeled an IF by a conductive wire. The energy spectra of the refractive index, extinction coefficient (absorption cross-section), energy loss and reflectivity functions for different photon polarizations, with strong anisotropy with respect to the system axis, were calculated ab initio for polyglycine a-helix molecule containing 1000 glycine residues. Strong anisotropy of these parameters was explained by photons interacting with different electronic transitions. Note that similarly strong anisotropy was also obtained for the optical absorption cross-sections in the simplified model. Both modeling approaches were used for calculating the absorption cross sections of interest. As a result, the absorption cross-section for photons propagating axially along MC IFs was much larger than their geometrical cross-section. The latter result was explained taking into account the density of electronic states, with numerous electrons contributing to the transition intensity at a given energy. We found that the simple conductive wire model describes the MC IF absorption spectrum better than the ab initio spectra. The latter conclusion was explained by the limitations of ab initio analysis, which only took into account one alpha-helix with 1000 aminoacids, whereas each porcine Muller cell IF is assembled of thousands of protein molecules, reaching the total length of ca. 100 mu m. The presently reported results contribute to the understanding of the quantum mechanism of high-contrast vision of vertebrate eyes. Published by Elsevier B.V.
dc.description.versioninfo:eu-repo/semantics/publishedVersion
dc.identifier.doi10.1016/j.saa.2020.118452
dc.identifier.issn1386-1425
dc.identifier.urihttp://hdl.handle.net/10400.1/16395
dc.language.isoeng
dc.peerreviewedyes
dc.publisherElsevier
dc.subjectAb initio
dc.subjectOptical parameters
dc.subjectAlpha-helix
dc.subjectAnisotropy
dc.subjectAbsorption cross-section
dc.subject.otherSpectroscopy
dc.titleAbsorption spectra of Muler cell intermediate filaments: experimental results and theoretical models
dc.typejournal article
dspace.entity.typePublication
oaire.citation.startPage118452
oaire.citation.titleSpectrochimica Acta Part A-Molecular and Biomolecular Spectroscopy
oaire.citation.volume238
person.familyNameKhmelinskii
person.givenNameIgor
person.identifier0000000420541031
person.identifier.ciencia-id0D1A-CB6C-6316
person.identifier.orcid0000-0002-6116-184X
person.identifier.ridC-9587-2011
person.identifier.scopus-author-id6701444934
rcaap.rightsrestrictedAccess
rcaap.typearticle
relation.isAuthorOfPublicationfcb9f09f-2e99-41fb-8c08-7e1acbc65076
relation.isAuthorOfPublication.latestForDiscoveryfcb9f09f-2e99-41fb-8c08-7e1acbc65076

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