title: The length of esterifying alcohol affects the aggregation properties of chlorosomal bacteriochlorophylls.
abstract: Chlorosomes, the main light-harvesting complexes of green photosynthetic bacteria, contain bacteriochlorophyll (BChl) molecules in the form of self-assembling aggregates. To study the role of esterifying alcohols in BChl aggregation we have prepared a series of bacteriochlorophyllide c (BChlide c) derivatives differing in the length of the esterifying alcohol (C(1), C(4), C(8) and C(12)). Their aggregation behavior was studied both in polar (aqueous buffer) and nonpolar (hexane) environments and the esterifying alcohols were found to play an essential role. In aqueous buffer, hydrophobic interactions among esterifying alcohols drive BChlide c derivatives with longer chains into the formation of dimers, while this interaction is weak for BChlides with shorter esterifying alcohols and they remain mainly as monomers. All studied BChlide c derivatives form aggregates in hexane, but the process slows down with longer esterifying alcohols due to competing hydrophobic interactions with hexane molecules. In addition, the effect of the length of the solvent molecules (n-alkanes) was explored for BChl c aggregation. With an increasing length of n-alkane molecules, the hydrophobic interaction with the farnesyl chain becomes stronger, leading to a slower aggregation rate. The results show that the hydrophobic interaction is the driving force for the aggregation in an aqueous environment, while in nonpolar solvents it is the hydrophilic interaction.
authors.affiliation: Biological Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic.
authors.forename: Anita
authors.initials: A
authors.lastname: Zupcanova
authors.forename: Juan B
authors.initials: JB
authors.lastname: Arellano
authors.forename: David
authors.initials: D
authors.lastname: Bina
authors.forename: Jiri
authors.initials: J
authors.lastname: Kopecky
authors.forename: Jakub
authors.initials: J
authors.lastname: Psencik
authors.forename: Frantisek
authors.initials: F
authors.lastname: Vacha
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D000473:Alkanes / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D001429:Bacteriochlorophylls / Q000737:chemistry*; D041883:Chlorobium / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004952:Esters / Q000737:chemistry*; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D013058:Mass Spectrometry; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry
chemical_list: D000438:Alcohols; D000473:Alkanes; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D004952:Esters; D045342:Light-Harvesting Protein Complexes; D014867:Water; C002084:bacteriochlorophyll c