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Multi-scale modeling of mycosubtilin lipopeptides at the air/water interface: structure and optical second harmonic generation

Abstract

Monolayers of the lipopeptide mycosubtilin are studied at the air/water interface. Their structure is investigated using molecular dynamics simulations. All-atom models suggest that the lipopeptide is flexible and aggregates at the interface. To achieve simulation times of several microseconds, a coarse-grained (CG) model based on the MARTINI force field was also used. These CG simulations describe the formation of half-micelles at the interface for surface densities up to 1 lipopeptide per nm2. In these aggregates, the tyrosine side chain orientation is found to be constrained: on average, its main axis, as defined along the C–OH bond, aligns along the interface normal and points towards the air side. The origin of the optical second harmonic generation (SHG) from mycosubtilin monolayers at the air/water interface is also investigated. The molecular hyperpolarizability of the lipopeptide is obtained from quantum chemistry calculations. The tyrosine side chain contribution to the hyperpolarizability is found to be dominant. The orientation distribution of tyrosine, associated with a dominant hyperpolarizability component along the C–OH bond of the tyrosine, yields a ratio of the susceptibility elements χ(2)ZZZ/χ(2)ZXX consistent with the experimental measurements recently reported by M. N. Nasir et al. [Phys. Chem. Chem. Phys., 2013, 15, 19919]. Previous Article | Next Article Paper Multi-scale modeling of mycosubtilin lipopeptides at the air/water interface: structure and optical second harmonic generation Claire Loison,*a Mehmet Nail Nasir,b Emmanuel Benichou,a Françoise Bessonb and Pierre-François Breveta Show Affiliations Phys. Chem. Chem. Phys., 2014,16, 2136-2148 DOI: 10.1039/C3CP53101E Received 23 Jul 2013, Accepted 27 Nov 2013 First published online 28 Nov 2013 | | Share on citeulike | Share on facebook | Share on twitter | | More PDF Rich HTML Buy PDF Add PDF to Basket (£38*) *Exclusive of taxes This article contains 13 page(s) Download Citation Help Request Permissions Access Denied Please choose one of the options provided in the log in section to gain access to this content: Abstract Cited by Related Content Metrics Monolayers of the lipopeptide mycosubtilin are studied at the air/water interface. Their structure is investigated using molecular dynamics simulations. All-atom models suggest that the lipopeptide is flexible and aggregates at the interface. To achieve simulation times of several microseconds, a coarse-grained (CG) model based on the MARTINI force field was also used. These CG simulations describe the formation of half-micelles at the interface for surface densities up to 1 lipopeptide per nm2. In these aggregates, the tyrosine side chain orientation is found to be constrained: on average, its main axis, as defined along the C–OH bond, aligns along the interface normal and points towards the air side. The origin of the optical second harmonic generation (SHG) from mycosubtilin monolayers at the air/water interface is also investigated. The molecular hyperpolarizability of the lipopeptide is obtained from quantum chemistry calculations. The tyrosine side chain contribution to the hyperpolarizability is found to be dominant. The orientation distribution of tyrosine, associated with a dominant hyperpolarizability component along the C–OH bond of the tyrosine, yields a ratio of the susceptibility elements χ(2)ZZZ/χ(2)ZXX consistent with the experimental measurements recently reported by M. N. Nasir et al. [Phys. Chem. Chem. Phys., 2013, 15, 19919].
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hal-01142523 , version 1 (15-04-2015)

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Claire Loison, Mehmet Nail Nasir, Emmanuel Benichou, Françoise Besson, Pierre-François Brevet. Multi-scale modeling of mycosubtilin lipopeptides at the air/water interface: structure and optical second harmonic generation. Physical Chemistry Chemical Physics, 2014, 16 (5), pp.2136-2148. ⟨10.1039/c3cp53101e⟩. ⟨hal-01142523⟩
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