Characterization of small unilamellar vesicles using solvatochromic π* indicators and particle sizing

Carrozzino, Jennifer M.; Fuguet, Elisabet; Helburn, Robin; Khaledi, Morteza G.

doi:10.1016/j.jbbm.2004.04.014

Cited by 11 publications

(10 citation statements)

References 32 publications

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“…The phospholipids were then resuspended in 20 mM phosphate buffer by vortex mixing. The resultant dispersed lipid, at a concentration of 0.5 mM with respect to phospholipids, was then sonicated and extruded through a 50 nm polycarbonate filter to obtain homogeneity in the size of vesicles ( − ).…”

Section: Methodsmentioning

confidence: 99%

Molecular Mechanisms that Govern the Specificity of Sushi Peptides for Gram-Negative Bacterial Membrane Lipids

et al. 2006

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Factor C-derived Sushi peptides (S1 and S3) have been shown to bind lipopolysaccharide (LPS) and inhibit the growth of Gram-negative bacteria but do not affect mammalian cells. On the premise that the composition of membrane phospholipids differs between the microbial and human cells, we studied the modes of interaction between S1 and S3 and the bacterial membrane phospholipids, POPG, in comparison to that with the mammalian cell membrane phospholipids, POPC and POPE. S1 exhibits specificity against POPG, suggesting its preference for bacterial anionic phospholipids, regardless of whether the phospholipids form vesicles in a solution or a monolayer on a solid surface. The specificity of the Sushi peptides for POPG is a consequence of the electrostatic and hydrophobic forces. The unsaturated nature of POPG confers fluidity to the lipid layer, and being in the proximity of LPS in the microenvironmental milieu, POPG probably enhances the insertion of the peptide-LPS complex into the bacterial inner membrane. Furthermore, during its interaction with POPG, the S1 peptide underwent a transition from random to alpha-helical coil, while S3 became a mixture of beta-sheet and alpha-helical structures. This differential structural change in the peptides could be responsible for their different modes of disruption of POPG vesicles. Conceivably, the selectivity for POPG spares the mammalian membranes from undesirable effects of antimicrobial peptides, which could be helpful in designing and developing a new generation of antibiotics and in offering some clues about the specific function of Factor C, a LPS biosensor.

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Section: Methodsmentioning

confidence: 99%

Molecular Mechanisms that Govern the Specificity of Sushi Peptides for Gram-Negative Bacterial Membrane Lipids

et al. 2006

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“…Development of reliable, accurate, and efficient methods for modeling of biologically active compounds, peptides, and proteins in phospholipid membranes is an important problem in computational chemistry. − During the association with membranes some parts of a large molecule may remain in water, while other parts enter into the milieu of different polarity, such as the water-rich interfacial lipid headgroup region or the hydrophobic acyl chain region. To model this process, the highly anisotropic environment of the lipid bilayer can be approximated by one or several slabs with different dielectric properties. , In a more realistic approach, the lipid bilayer may be described by continuous polarity profiles that can be obtained experimentally using different spectroscopic probes − or theoretically.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Solvent Model of the Lipid Bilayer. 1. Parameterization of Long-Range Electrostatics and First Solvation Shell Effects

Lomize

Pogozheva

Mosberg

2011

J. Chem. Inf. Model.

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A new implicit solvation model was developed for calculating free energies of transfer of molecules from water to any solvent with defined bulk properties. The transfer energy was calculated as a sum of the first solvation shell energy and the long-range electrostatic contribution. The first term was proportional to solvent accessible surface area and solvation parameters (σi) for different atom types. The electrostatic term was computed as a product of group dipole moments and dipolar solvation parameter (η) for neutral molecules, or using a modified Born equation for ions. The regression coefficients in linear dependencies of solvation parameters σi and η on dielectric constant, solvatochromic polarizability parameter π*, and hydrogen-bonding donor and acceptor capacities of solvents were optimized using 1269 experimental transfer energies from 19 organic solvents to water. The root-mean-square errors for neutral compounds and ions were 0.82 and 1.61 kcal/mol, respectively. Quantification of energy components demonstrates the dominant roles of hydrophobic effect for non-polar atoms and of hydrogen-bonding for polar atoms. The estimated first solvation shell energy outweighs the long-range electrostatics for most compounds including ions. The simplicity and computational efficiency of the model allows its application for modeling of macromolecules in anisotropic environments, such as biological membranes.

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“…For consistency in comparison of values, we have re-determined Às for the well characterized small molecule probes (1a-b and 2a) using the same solvent list (Tables 2-4); these values compare favorably with those of Kamlet et al 1 Table 5 summarizes all Às values for indicators in this work computed to date, including some previously published seven-point determinations. 4,8 We suggest that the conformational effects proposed for 1e-f in the solvent mesitylene, which resulted in an outlier point for selected spectral bands ( Fig. 6-1d) on LSERs for those dyes, may also manifest themselves in the region of the LSER that corresponds to v max for linear alkane solvents (p Ã 0.00).…”

Section: Lsers and Trends In Ssmentioning

confidence: 86%

“…Among the more recent developments is the synthesis and application of indicators with increasingly long hydrophobic tails that permit the probing of solvent environments inside micelles and lipid bilayers, thus extending p Ã measurements to these more complex organic interfacial systems for which there is considerable interest. [6][7][8][9][10][11] In this work, we present and compare the solvatochromic properties of two of the more hydro-phobic forms that we have prepared. They are the long chain N,N-dialkyl-4-nitroanilines and some long chain alkyl 4-nitrophenyl ethers (Figs 1 and 2).…”

Section: Introductionmentioning

confidence: 99%

Solvatochromic properties of long alkyl chain π* indicators: comparison of N,N‐dialkyl‐4‐nitroanilines and alkyl 4‐nitrophenyl ethers

Helburn¹,

Bartoli²,

Pohaku³

et al. 2007

J of Physical Organic Chem

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Hydrophobic forms of the N,N-dialkyl-4-nitroaniline (DNAP) ( p-O 2 NC 6 H 4 NR 2 ) (1a-f) and alkyl-4nitrophenyl ether ( p-O 2 NC 6 H 4 OR) (2a-c) solvatochromic p Ã indicators have been characterized and compared with respect to: (a) solvatochromic bandshape, (b) sensitivity expressed as Ss, (dv max /dp Ã ), and (c) trends in Às with increasing length of alkyl chain(s) on the probe molecule. -Octyl 4-nitrophenyl ether ( p-O 2 NC 6 H 4 OC 8 H 17 ) (2b) and -decyl 4-nitrophenyl ether ( p-O 2 N C 6 H 4 OC 10 H 21 ) (2c) were synthesized and their solvatochromic UV/Vis absorption bands were found to maintain a Gausso-Lorentzian bandshape for the indicators in non-polar and alkyl substituted aromatic solvents, for example, hexane(s) and mesitylene. Corresponding absorption bands for 1a-f display increasing deviation from a Gausso-Lorentzian shape in the same solvents as the alkyl chains on the indicator are increased in length all the way to C 10 and C 12 , for example, N,N-didecyl-4-nitroaniline ( p-O 2 NC 6 H 4 N (C 10 H 21 ) 2 ) and N,N-didodecyl-4-nitroaniline ( p-O 2 NC 6 H 4 N (C 12 H 25 ) 2 ) (1d-f). A plot of Às versus C n follows a 1st order decay for the DNAP indicators but is linear for the alkyl 4-nitrophenyl ethers. A discussion of how the long alkyl chains on the two types of indicators affect the orientation and overlap of n and p Ã orbitals, and resulting solvatochromic bands is presented. For DNAP, overextending the alkyl chains to obtain greater hydrophobic character may cause the alkane component to dominate solute-solvation processes at the expense of the probe's fundamental solvatochromic character. a Range of Chi-square ¼ 9.5 Â 10 À6 to 4.0 Â 10 À5 ; range of r 2 ¼ 0.9539 to 0.9886. b Range of Chi-square ¼ 9.3 Â 10 À6 to 4.5 Â 10 À5 ; range of r 2 ¼ 0.9489 to 0.9893. c Range of Chi-square ¼ 7.10 Â 10 À6 to 5.0 Â 10 À5 ; range of r 2 ¼ 0.9037 to 0.9923. d Range of Chi-square ¼ 7.15 Â 10 À6 to 6.0 Â 10 À5 ; Range of r 2 ¼ 0.9152 to 0.9919. e Values are for cyclohexane. f Values are for the cyclic ether dioxane. Figure 4. Solvatochromic (UV/Vis) absorption bands of 2a (left) and 2c (right) in hexane(s)

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Characterization of small unilamellar vesicles using solvatochromic π* indicators and particle sizing

Cited by 11 publications

References 32 publications

Molecular Mechanisms that Govern the Specificity of Sushi Peptides for Gram-Negative Bacterial Membrane Lipids

Molecular Mechanisms that Govern the Specificity of Sushi Peptides for Gram-Negative Bacterial Membrane Lipids

Anisotropic Solvent Model of the Lipid Bilayer. 1. Parameterization of Long-Range Electrostatics and First Solvation Shell Effects

Solvatochromic properties of long alkyl chain π* indicators: comparison of N,N‐dialkyl‐4‐nitroanilines and alkyl 4‐nitrophenyl ethers

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