7 ± 1.4 mM for 1:10 1-hydroxypyrene samples. Error bars represent standard deviations Permeability Assays The influence of PAHs on the permeability of fatty acid bilayers to sucrose and KCl was measured using UV–vis spectrophotometry. Initial rates were determined selleck chemicals by extrapolating to zero (time of solute injection) and determining the slope of the curve. The data matched an exponential decay curve

with R2 ≥ 0.995. Figure 5 shows permeability assays for a pure fatty acid sample and a sample with 1:10 1-hydroxypyrene. Permeability of the membranes to both KCl and sucrose was significantly decreased by incorporation of 1-hydroxypyrene. The initial rates for permeability to KCl of different PAH incorporations are shown in Fig. 6 (values are based on ≥ 3 samples). Fig. 5 Permeability assays of a 60 mM DA + FA mix sample (top) and a 1:10 1-hydroxypyrene sample (bottom). Injection of 0.1 M of solute

at t = 20 s. The absorbance decrease due to swelling of vesicles by solute passing the membrane is significantly slower in the 1-hydroxypyrene samples Fig. 6 Initial rates of absorbance loss due to reswelling PLX-4720 in vitro of vesicles by KCl permeation of a 60 mM DA + FA mix, 1:10 9-ACA + FA mix and a 1:10 1-hydroxypyrene + FA mix sample. Values are calculated by fitting data to exponential decay and extrapolating to t = 20 s (time of solute injection). Error bars represent standard deviations Both 1-hydroxypyrene and 9-anthracene carboxylic acid significantly decreased the permeability of fatty acid membranes to KCl by 4.2- and 2.5-fold, respectively. Permeability coefficients for sucrose

were determined according to Chakrabarti & Deamer (1992). The interior solute concentration of vesicles obeys A(t)int = A(eq)int (1-eλt), where A(t)int is the interior concentration of solute at time t, A(eq)int is the interior solute concentration at t = infinity and λ is the decay rate. Since 0.1 M of solute is added and the osmotic gradient should disappear at 4��8C Aint = Aex, A(eq)int can be assumed to be 0.1 M (the total interior volume of the vesicles is negligible compared to the volume of bulk medium), so A(t)int = 0.1–0.1*e-t/τ. The mean lifetime (τ) can be obtained directly from fitting the data to exponential decay, and permeability coefficients can be obtained by P = (r/3) λ. Figure 7 shows the measured coefficients. Fig. 7 Permeability coefficients of sucrose calculated by determination of the decay constant by fitting the data to exponential decay. The permeability coefficient is lowered ~4 fold by 1-hydroxypyrene incorporation. Error bars represent standard deviations Discussion PAHs are present in many space environments and likely contributed to the carbon inventory on the early Earth delivered during the heavy bombardment phase through impacts of small solar system bodies (Chyba and Sagan 1992; Gomes et al. 2005), as well as abiotic synthesis on the early Earth.