scholarly journals Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

2021 ◽  
Author(s):  
Yigal Lahav ◽  
Dror Noy ◽  
Igor Schapiro
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Binding Proteins ◽  
Water Soluble ◽  
Spectral Tuning ◽  
Photosynthetic Complexes ◽  
Protein Environment ◽  
Ring Deformation

: In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from Brassicaceae (WSCPs) are useful for...

scholarly journals Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

2020 ◽  
Author(s):  
Yigal Lahav ◽  
Dror Noy ◽  
Igor Schapiro
Keyword(s):  
Absorption Spectra ◽  
Conformational Dynamics ◽  
Spectral Shift ◽  
Water Soluble ◽  
Conformational Sampling ◽  
Protein Electrostatics ◽  
Spectral Tuning ◽  
Photosynthetic Complexes ◽  
Artificial Protein ◽  
Ring Deformation

In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from <i>Brassicaceae</i> (WSCPs) are useful for studying spectral tuning mechanisms due to their symmetric homotetramer structure, the ability to rigorously modify the chlorophyll’s protein surroundings, and the availability of crystal structures. Here, we present a rigorous analysis based on hybrid Quantum Mechanics and Molecular Mechanics simulations with conformational sampling to quantify the relative contributions of steric and electrostatic factors to the absorption spectra of WSCP-chlorophyll complexes. We show that when considering conformational dynamics, chlorophyll ring deformation accounts for about one-third of the spectral shift, whereas protein electrostatics accounts for the remaining two-thirds. From a practical perspective, protein electrostatics is easier to manipulate than chlorophyll conformations, thus, it may be more readily implemented in designing artificial protein-chlorophyll complexes with desired spectral shift.

scholarly journals Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

2020 ◽  
Author(s):  
Yigal Lahav ◽  
Dror Noy ◽  
Igor Schapiro
Keyword(s):  
Absorption Spectra ◽  
Conformational Dynamics ◽  
Spectral Shift ◽  
Water Soluble ◽  
Conformational Sampling ◽  
Protein Electrostatics ◽  
Spectral Tuning ◽  
Photosynthetic Complexes ◽  
Artificial Protein ◽  
Ring Deformation

In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from <i>Brassicaceae</i> (WSCPs) are useful for studying spectral tuning mechanisms due to their symmetric homotetramer structure, the ability to rigorously modify the chlorophyll’s protein surroundings, and the availability of crystal structures. Here, we present a rigorous analysis based on hybrid Quantum Mechanics and Molecular Mechanics simulations with conformational sampling to quantify the relative contributions of steric and electrostatic factors to the absorption spectra of WSCP-chlorophyll complexes. We show that when considering conformational dynamics, chlorophyll ring deformation accounts for about one-third of the spectral shift, whereas protein electrostatics accounts for the remaining two-thirds. From a practical perspective, protein electrostatics is easier to manipulate than chlorophyll conformations, thus, it may be more readily implemented in designing artificial protein-chlorophyll complexes with desired spectral shift.

scholarly journals Light absorption by organic carbon from wood combustion

2010 ◽  
Vol 10 (4) ◽  
pp. 1773-1787 ◽  
Author(s):  
Y. Chen ◽  
T. C. Bond
Keyword(s):  
Organic Carbon ◽  
Radiative Transfer ◽  
Absorption Spectra ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Water Soluble ◽  
Clear Sky ◽  
Wood Temperature ◽  
Visible Wavelengths ◽  
Positive Direct

Abstract. Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While black carbon (BC) is highly absorbing, some organic carbon (OC) also has significant absorption, especially at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to positive direct aerosol radiative forcing. Quantification of that absorption is necessary so that radiative-transfer models can evaluate the net radiative effect of OC. In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble OC contributes to light absorption at both ultraviolet and visible wavelengths. However, a larger portion of the absorption comes from OC that is extractable only by methanol. Absorption spectra of water-soluble OC are similar to literature reports. We compare spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating OC with higher absorption; changing wood temperature from a devolatilizing state of 210 °C to a near-flaming state of 360 °C causes about a factor of four increase in mass-normalized absorption at visible wavelengths. A clear-sky radiative transfer model suggests that, despite the absorption, both high-temperature and low-temperature OC result in negative top-of-atmosphere radiative forcing over a surface with an albedo of 0.19 and positive radiative forcing over bright surfaces. Unless absorption by real ambient aerosol is higher than that measured here, it probably affects global average clear-sky forcing very little, but could be important in energy balances over bright surfaces.

Linearly polarized light absorption spectra of chlorosomes, light-harvesting antennas of photosynthetic green sulfur bacteria

2010 ◽  
Vol 484 (4-6) ◽  
pp. 333-337 ◽  
Author(s):  
Hitoshi Tamiaki ◽  
Shingo Tateishi ◽  
Shosuke Nakabayashi ◽  
Yutaka Shibata ◽  
Shigeru Itoh
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Light Harvesting ◽  
Polarized Light ◽  
Green Sulfur Bacteria ◽  
Sulfur Bacteria ◽  
Linearly Polarized ◽  
Green Sulfur

Disparate effects of two phosphatidylcholine binding proteins, C-reactive protein and surfactant protein A, on pulmonary surfactant structure and function

2004 ◽  
Vol 287 (6) ◽  
pp. L1145-L1153 ◽  
Author(s):  
Kaushik Nag ◽  
Karina Rodriguez-Capote ◽  
Amiya Kumar Panda ◽  
Laura Frederick ◽  
Stephen A. Hearn ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Amorphous Material ◽  
Protein A ◽  
Surfactant Protein ◽  
Water Soluble ◽  
Surfactant Protein A ◽  
Surface Films ◽  
Inhibitory Effects ◽  
C Reactive Protein ◽  
Reactive Protein

C-reactive protein (CRP) and surfactant protein A (SP-A) are phosphatidylcholine (PC) binding proteins that function in the innate host defense system. We examined the effects of CRP and SP-A on the surface activity of bovine lipid extract surfactant (BLES), a clinically applied modified natural surfactant. CRP inhibited BLES adsorption to form a surface-active film and the film's ability to lower surface tension (γ) to low values near 0 mN/m during surface area reduction. The inhibitory effects of CRP were reversed by phosphorylcholine, a water-soluble CRP ligand. SP-A enhanced BLES adsorption and its ability to lower γ to low values. Small amounts of SP-A blocked the inhibitory effects of CRP. Electron microscopy showed CRP has little effect on the lipid structure of BLES. SP-A altered BLES multilamellar vesicular structure by generating large, loose bilayer structures that were separated by a fuzzy amorphous material, likely SP-A. These studies indicate that although SP-A and CRP both bind PC, there is a difference in the manner in which they interact with surface films.

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