Abstract:In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while "psi-type" CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samp… Show more
“…For the case of isolated granal membranes, where the extensive vertical stacking of the membranes is lost, the observed characteristic excitonic CD signals are very similar to those found for unstacked thylakoid membranes (46). In this highly complex system it is difficult to discriminate the contribution of the different components, because the CD spectra of BBY membranes are largely dominated by the CD features of the LHCII molecules (46). The signal appearing at 650 nm is attributable to short-range chl b related interactions within LHCII complexes either in isolated state or in both BBY and intact thylakoid membranes (47)(48)(49); therefore, the 610/646 nm band in our BBY membrane preparations can be used as a fingerprint of LHCII stability.…”
Section: Thermal Stability Of Bby Membranes At Two Different States Osupporting
confidence: 71%
“…The short-and long-range pigment-pigment interactions serve as fingerprints of the supramolecular organization and conformational stability of the complexes in photosynthetic membranes (45). For the case of isolated granal membranes, where the extensive vertical stacking of the membranes is lost, the observed characteristic excitonic CD signals are very similar to those found for unstacked thylakoid membranes (46). In this highly complex system it is difficult to discriminate the contribution of the different components, because the CD spectra of BBY membranes are largely dominated by the CD features of the LHCII molecules (46).…”
Section: Thermal Stability Of Bby Membranes At Two Different States Omentioning
Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching.
“…For the case of isolated granal membranes, where the extensive vertical stacking of the membranes is lost, the observed characteristic excitonic CD signals are very similar to those found for unstacked thylakoid membranes (46). In this highly complex system it is difficult to discriminate the contribution of the different components, because the CD spectra of BBY membranes are largely dominated by the CD features of the LHCII molecules (46). The signal appearing at 650 nm is attributable to short-range chl b related interactions within LHCII complexes either in isolated state or in both BBY and intact thylakoid membranes (47)(48)(49); therefore, the 610/646 nm band in our BBY membrane preparations can be used as a fingerprint of LHCII stability.…”
Section: Thermal Stability Of Bby Membranes At Two Different States Osupporting
confidence: 71%
“…The short-and long-range pigment-pigment interactions serve as fingerprints of the supramolecular organization and conformational stability of the complexes in photosynthetic membranes (45). For the case of isolated granal membranes, where the extensive vertical stacking of the membranes is lost, the observed characteristic excitonic CD signals are very similar to those found for unstacked thylakoid membranes (46). In this highly complex system it is difficult to discriminate the contribution of the different components, because the CD spectra of BBY membranes are largely dominated by the CD features of the LHCII molecules (46).…”
Section: Thermal Stability Of Bby Membranes At Two Different States Omentioning
Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching.
“…On the other hand, it is known that the magnitude of psi-type CD in granal thylakoids is considerably weaker than in microcrystalline LHCII ( Fig. 16.2 ; Simidjiev et al 1997 ;Miloslavina et al 2012 ). Taken together, the available electron microcopy and CD data strongly suggest that the stacked regions contain large ordered arrays of ( super -) complexes , but the overall long -range order is probably weaker than in the semicrystalline domains .…”
Section: B Ordered Arrays Of Protein Complexesmentioning
“…This section compares the CD and ACD spectra of isolated LHCII in aggregated state and in reconstituted membranes, oriented by different methods. Whereas the psi-type ACD of lamellar macroaggregates in compressed gels has been reported earlier [69,162], purely excitonic ACD spectra of LHCII have not been published yet.…”
Section: Anisotropic Circular Dichroism Of Lhciimentioning
confidence: 88%
“…the CD of molecules with fixed macroscopic space orientation [67,68]. For example, in an ideal case, by measuring the CD of the dimer separately with light propagating along the x and y coordinate axes, one could extract the individual exciton CD bands [69] and hence obtain direct physical parameters, such as the orientation of the excitonic transition dipole moments or the coupling energy (from the difference in the bands' central frequencies), which are not accessible from ordinary CD measurements.…”
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