Rhizomorph Formation in Fungi

The effect on growth and rhizomorph formation of 12 alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, tert-butyl alcohol, 1-pentanol, iso-amyl alcohol, ethylene glycol and glycerol) at different concentrations has been examined for 2 isolates of Armillaria mellea (Vahl ex Fr.) Quél. and 1 of Clitocybe geotropa (Bull. ex Fr.) Quél. The fungi were cultivated for 28 days on a synthetic, liquid glucose medium with the alcohols as supplement. The following alcohols strongly stimulated growth and rhizomorph formation: ethanol, 1-propanol and 1-butanol. A great variation was demonstrated between the isolates in relation to rhizomorph production, morphology, and ability to be stimulated by different alcohols.     

The interaction of alcohol radicals with human hemoglobin

Aqueous deoxyhemoglobin solutions (2 mg/ml) were gamma-irradiated by a⁶⁰Co source in the presence of methanol, ethanol, 1-butanol andt-butanol under N₂O or argon. The effects of the interaction of the particular alcohol radical species with hemoglobin were determined according to the detected spectral alterations in the visible range. The amounts of stable final products in the form of methemoglobin (MetHb) and the sum of hemichromes and cholehemichromes (Hemichr) were estimated in irradiated preparations. For preparations irradiated under N₂O, the radiation yield for MetHb formation was threefold lower in the presence of ethanol and 1-butanol [G(MetHb)=0.33] compared with preparations irradiated in the presence oft-butanol or without alcohol [G(MetHb)=1.00]. The yield of hemichromes and cholehemichromes in preparations irradiated under N2O increased in the order: ethanol (G=0.38), 1-butanol (G=0.52),t-butanol (G=0.59), and in the absence of alcohol (G=0.72). The high effectivity oft-butanol radicals for iron oxidation and Hb destruction is apparently due to their oxidative properties, compared with the other radicals. It was also shown that ethanol radicals reduce MetHb 10 times more effectively [G(Fe(II)) = 2.5] compared witht-butanol radicals [G(Fe(II)) = 0.24]. For samples irradiated under argon all the observed changes were similar, regardless of the presence of alcohols. This effect can be attributed to reconstruction reactions of Hb molecules in the presence of both oxidizing (OH ort-but·) and reducing agents (e _aq ^/– ). The following sequence of effectivities of water radiolysis products and secondary alcohol radicals for hemoglobin destruction has been identified: meth·, eth·1-but·e _aq ^/– t-but··OH.This work was supported by State Committee for Scientific Research (Poland), grant no. 44509203     

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Redox interactions between catalase and alcohol dehydrogenase pathways of ethanol metabolism in the perfused rat liver

Alcohol metabolism via alcohol dehydrogenase (ADH) and catalase was studied in perfused rat livers by measuring the oxidation of methanol and butanol, selective substrates for catalase and ADH, respectively. In livers from fasted rats, basal rates of methanol uptake of 15 +/- 1 mumol/g/h were decreased significantly to 8 +/- 2 mumol/g/h by addition of butanol. Concomitantly, pyridine nucleotide fluorescence detected from the liver surface was increased by butanol but not methanol. Both effects of butanol were blocked by an inhibitor of ADH, 4-methylpyrazole, consistent with the hypothesis that elevation of the NADH redox state by butanol inhibited H2O2 production via NAD+-requiring peroxisomal beta-oxidation, leading indirectly to diminished rates of catalase-dependent methanol uptake. In support of this idea, both butanol and butyraldehyde inhibited H2O2 generation. The NADH redox state was also elevated by xylitol, causing a 75% decrease in rates of methanol uptake by livers from fasted rats. This effect was not observed in livers from fed rats unless malate-aspartate shuttle activity was reduced by infusion of the transaminase inhibitor aminooxyacetate. Taken together, these data indicate that generation of reducing equivalents from ADH in the cytosol inhibits H2O2 generation leading to significantly diminished rates of peroxidation of alcohols via catalase. This phenomenon may represent an important physiological mechanism of regulation of ethanol oxidation in intact cells.     

Hepatic microsomal alcohol-oxidizing system. Affinity for methanol, ethanol, propanol, and butanol.

Oxidation of methanol, ethanol, propanol, and butanol by the microsomal fraction of rat liver homogenate is described. This microsomal alcohol-oxidizing system is dependent on NADPH and molecular oxygen and is partially inhibited by CO, features which are common for microsomal drug-metabolizing enzymes. The activity of the microsomal alcohol-oxidizing system could be dissociated from the alcohol peroxidation via catalase-H2O2 by differences in substrate specificity, since higher aliphatic alcohols react only with the microsomal system, but not with catalase-H2O2. Following solubilization of microsomes by ultrasonication and treatment with deoxycholate, the activity of the microsomal alcohol-oxidizing system was separated from contaminating catalase by DEAE-cellulose column chromatography, ruling out an obligatory involvement of catalase-H2O2 in the activity of the NADPH-dependent microsomal alcohol-oxidizing system. In intact hepatic microsomes, the catalase inhibitor sodium azide slightly decreased the oxidation of methanol and ethanol, but not that of propanol and butanol, indicating a facultative role of contaminating catalase in the microsomal oxidation of lower aliphatic alcohols only. It is suggested that the microsomal alcohol-oxidizing system accounts, at least in part, for that fraction of hepatic alcohol metabolism which is independent of the pathway involving alcohol dehydrogenase activity.     

Comparative study of the effect of aliphatic alcohols on energy-dependent accumulation of Ca2+ in intracellular membranes of smooth muscle cells

The effects of ethanol and other aliphatic alcohols on energy-dependent Ca2+ transport in endoplasmic reticulum and mitochondria were studied in digitonin-treated myometrium cells. The Ca2+ uptake in mitochondria increased (on 15-20%) with increasing methanol, ethanol and propanol concentrations in medium, whereas further rise of concentration inhibited this process. Treatments of myometrial cells with short-chain alcohols caused an inhibition of calcium uptake in endoplasmic reticulum. Butanol inhibited both calcium uptake in mitochondria and endoplasmic reticulum. Ca2+ accumulation in intracellular pools is inhibited by aliphatic alcohols in the following order of potency: butanol > propanol > ethanol > methanol. It is concluded that modifying effect of aliphatic alcohols on energy dependent calcium accumulation in intracellular membrane structures is defined as on origin of Ca(2+)-transporting system and (or) properties of these membrane structures so on properties of alcohols.     

Effects of alcohols on the respiration and fermentation of aerated suspensions of baker's yeast.

The immediate effects of externally added alcohols on CO2 production and O2 consumption of suspensions of washed, aerated baker's yeast were studied by stopped-flow membrane inlet mass spectrometry. Glucose-supported fermentation was progressively inhibited by increasing ethanol concentration (0-20%, v/v). The inhibition by ethanol was quite different from that observed for acetaldehyde; thus it is unlikely that toxicity of the latter can account for the observed effects. For five different alkanols (methanol, ethanol, 1-propanol, 2-propanol and 1-butanol) increasing inhibition of anaerobic fermentation was correlated with increased partition coefficients into a hydrophobic milieu. This suggests that the action of ethanol is primarily located at a hydrophobic site, possibly at a membrane. Results for respiratory activities were not as definite as for those for anaerobic metabolism because some alkanols act as respiratory substrates as well as giving inhibitory effects.     

Inhibitory effects of alcohols on thermolysin activity as examined using a fluorescent substrate

Alcohols inhibit the thermolysin-catalyzed hydrolysis of N-[3-(2-furyl)acryloyl]-Gly-L-Leu-NH(2) and decrease the NaCl-induced activation of thermolysin in a concentration-dependent manner [K. Inouye et al. (1997) J. Biochem. 122, 358-364]. In this study, the inhibitory effects of alcohols on thermolysin activity were examined in detail using 10 different alcohols and a fluorescent substrate, (7-methoxycoumarin-4-yl) acetyl-L-Pro-L-Leu-Gly-L-Leu-[N(3)-(2,4-dinitrophenyl)-L-2,3-diamino-propionyl]-L-Ala-L-Arg-NH(2). The inhibition by all alcohols examined is completely reversible, and thermolysin activity is recovered by dilution. The inhibitor constants (K(i)) are in the range of 35-430 mM, and the order of the inhibitory effect is 1-pentanol, 1-propanol, 2-butanol, 2-methyl-1-propanol > 1-butanol > 2-propanol > ethanol, tert-amyl alcohol > tert-butyl alcohol > methanol. Linear and secondary alcohols whose mains chains consist of more than 3 carbons inhibit thermolysin effectively. Thermolysin activity is decreased by decreasing the dielectric constant, D, of the reaction medium containing the alcohol, and the decrease depending on the D value was almost the same manner for all alcohols except methanol, tert-butyl alcohol, and tert-amyl alcohol. Alcohols may inhibit thermolysin activity both by binding to the active site, most possibly to the S1' subsite, of thermolysin and by altering the electrostatic and hydrophobic environment around the thermolysin molecule.     

Effect of short-chain primary alcohols on fluidity and activity of sarcoplasmic reticulum membranes

Intramolecular excimer formation with the fluorescent probe 1,3-di(1-pyrenyl)propane, differential scanning calorimetry, and X-ray diffraction were used to assess the effect of ethanol, 1-butanol, and 1-hexanol on the bilayer organization in model membranes, sarcoplasmic reticulum (SR) lipids and native SR membranes. These alcohols have fluidizing effects on membranes and lower the main transition temperature of dimyristoylphosphatidylcholine (DMPC), but only 1-hexanol alters the cooperativity of the phase transition and significantly increases the thickness of DMPC bilayers. The interaction of the three alcohols with the SR Ca2+ pump was also investigated. Hydrolysis of ATP and coupled Ca2+ uptake are differently sensitive to the three alcohols. Whereas ethanol and 1-butanol inhibited the Ca2+ uptake, 1-hexanol stimulated it. Nevertheless, the energetic efficiency of the pump (Ca2+/ATP) is not significantly affected by ethanol or 1-hexanol, but uncoupling was observed with 1-butanol at high concentrations. The different effects of alcohols on the activity of SR membranes rule out an unitary mechanism of action on the basis of fluidity changes induced in the lipid bilayer. Depending on the chain length, the alcohols interact with the SR membranes in different domains, perturbing differently the Ca2+-pump activity.     

Alcohols enhance caerulein-induced zymogen activation in pancreatic acinar cells

Activation of zymogens within the pancreatic acinar cell is an early feature of acute pancreatitis. Supraphysiological concentrations of cholecystokinin (CCK) cause zymogen activation and pancreatitis. The effects of the CCK analog, caerulein, and alcohol on trypsin and chymotrypsin activation in isolated pancreatic acini were examined. Caerulein increased markers of zymogen activation in a time- and concentration-dependent manner. Notably, trypsin activity reached a peak value within 30 min, then diminished with time, whereas chymotrypsin activity increased with time. Ethanol (35 mM) sensitized the acinar cells to the effects of caerulein (10(-10) to 10(-7) M) on zymogen activation but had no effect alone. The effects of ethanol were concentration dependent. Alcohols with a chain length of >or=2 also sensitized the acinar cell to caerulein; the most potent was butanol. Branched alcohols (2-propanol and 2-butanol) were less potent than aliphatic alcohols (1-propanol and 1-butanol). The structure of an alcohol is related to its ability to sensitize acinar cells to the effects of caerulein on zymogen activation.     

Induction of l-lysine ɛ-aminotransferase by l-lysine in Streptomyces clavuligerus, producer of cephalosporins

Abstract Several alcohols were examined as substrates for the polyhydroxyalkanoate synthesis by Paracoccus denitrificans. The bacterium synthesized a homopolyester of poly(3-hydroxybutyrate) from ethanol. When n -pentanol was used as growth substrate, homopolyester poly(3-hydroxyvalerate) was synthesized, whereas copolyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) accumulated during bacterial growth on n -propanol. When alcohols were automatically fed as growth substrates, ethanol, n -propanol, and n -pentanol gave higher polyester content. Although poly(3-hydroxybutyrate) was synthesized from methanol or n -butanol, its content was very low. Under nitrogen-deficient conditions, polyester;content in cells increased, especially with ethanol, n -propanol, and n -pentanol. Using a mixture of two alcohols P. denitrificans could synthesize polyesters with varying relative ratios of 3-hydroxybutyrate to 3-hydroxyvalerate.     

Close Correlation between Heat Shock Response and Cytotoxicity in Neurospora crassa Treated with Aliphatic Alcohols and Phenols

In Neurospora crassa the aliphatic alcohols methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, ethylene glycol, glycerol, and allyl alcohol and the phenolic compounds phenol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, sodium salicylate, and acetylsalicylic acid were analyzed with respect to their capacities to induce heat shock proteins (HSP) and to inhibit protein synthesis. Both the alcohols and phenols showed the greatest levels of HSP induction at concentrations which inhibited the overall protein synthesis by about 50%. The abilities of the different alcohols to induce the heat shock response are proportional to their lipophilicities: the lipophilic alcohol isobutanol is maximally inductive at about 0.6 M, whereas the least lipophilic alcohol, methanol, causes maximal induction at 5.7 M. The phenols, in general, show a higher capability to induce the heat shock response. The concentrations for maximal induction range between 25 mM (sodium salicylate) and 100 mM (resorcinol). Glycerol (4.1 M) shifted the concentration necessary for maximal HSP induction by hydroquinone from 50 to 200 mM. The results reveal that the induction of HSP occurs under conditions which considerably constrain cell metabolism. The heat shock response, therefore, does not represent a sensitive marker for toxicity tests but provides a good estimate for the extent of cell damage.     

Oxidation of secondary alcohols to methyl ketones by yeasts.

Cell suspensions of yeasts, Candida utilis ATCC 26387, Hansenula polymorpha ATCC 26012, Pichia sp. NRRL-Y-11328, Torulopsis sp. strain A1, and Kloeckera sp. strain A2, grown on various C-1 compounds (methanol, methylamine, methylformate), ethanol, and propylamine catalyzed the oxidation of secondary alcohols to the corresponding methyl ketones. Thus, isopropanol, 2-butanol, 2-pentanol, and 2-hexanol were converted to acetone, 2-butanone, 2-pentanone, and 2-hexanone, respectively. Cell-free extracts derived from methanol-grown yeasts catalyzed an oxidized nicotinamide adenine dinucleotide-dependent oxidation of secondary alcohols to the corresponding methyl ketones, Primary alcohols were not oxidized. The effect of various environmental factors on the production of methyl ketones from secondary alcohols by methanol-grown Pichia sp. was investigated.     

beta-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus: structure and activity in the presence of alcohols.

beta-Glycosidase from the extreme thermophilic archaeon Sulfolobus solfataricus is a tetrameric protein with a molecular mass of 240 kDa, stable in the presence of detergents, and with a maximal activity at temperatures above 95 degrees C. Understanding the structure-activity relationships of the enzyme under different conditions is of fundamental importance for both theoretical and applicative purposes. In this paper we report the effect of methanol, ethanol, 1-propanol, and 1-butanol on the activity of S. solfataricus beta-glycosidase expressed in Escherichia coli. The alcohols stimulated the enzyme activity, with 1-butanol producing its maximum effect at a lower concentration than the other alcohols. The structure of the enzyme was studied in the presence of 1-butanol by circular dichroism, and Fourier-transform infrared and fluorescence spectroscopies. Circular dichroism and steady-state fluorescence measurements revealed that at low temperatures the presence of the alcohol produced no significant changes in the tertiary structure of the enzyme. However, time-resolved fluorescence data showed that the alcohol modifies the protein microenvironment, leading to a more flexible enzyme structure, which is probably responsible for the enhanced enzymatic activity.     

Flow calorimetry of the sorption of butanols to elastin preparations and comparison with surface areas determined by krypton-85 adsorption

1. The apparent surface areas of elastin samples as well as of several other fibrous protein preparations (collagen, keratin, polymeric stroma of aorta) were determined using two different approaches: (a) the Brunauer-Emmett-Teller method with 85Kr and (b) microflow calorimetry with n- and tert.-butanol as adsorbents in a heptane stream. 2. Areas of heat signals obtained by flow calorimetry for the adsorption and desorption of n- and tert.-butanol were substantially equivalent; desorption was more protracted than adsorption, the difference between the speed of desorption and adsorption increased with decreasing chain length of the alcohols (methanol, ethanol, n-propanol and n-butanol). 3. An inverse linear relationship was found between the energy change recorded during the adsorption process and the chain length of the alcohols (methanol, ethanol, n-propanol, n-butanol). 4. Heats of adsorption of tert.-butanol were systematically found to be significantly lower than those of n-butanol with all the protein samples investigated. 5. The apparent surface areas of the protein samples determined with tert.-butanol were on the average of the same order or only slightly higher than those obtained with 85Kr. Results obtained with n-butanol were significantly higher. The difference between surface areas obtained with n- and tert.-butanol depended on the nature of the protein sample, on its method of preparation and to some extent on the residual humidity of the sample. 6. The results could be explained on the basis of the hydrophobic theory of elastin structure (see ref. 4) and confirmed our former conclusions (see ref. 3) concerning the significantly higher surface areas of elastin samples purified by different procedures as compared to collagen or to keratin. They also confirmed the accessibility of the surface of elastic fibers to the molecular probes used in the polymeric stroma of aorta.     

Oxidation of secondary alcohols to methyl ketones by yeasts.

Cell suspensions of yeasts, Candida utilis ATCC 26387, Hansenula polymorpha ATCC 26012, Pichia sp. NRRL-Y-11328, Torulopsis sp. strain A1, and Kloeckera sp. strain A2, grown on various C-1 compounds (methanol, methylamine, methylformate), ethanol, and propylamine catalyzed the oxidation of secondary alcohols to the corresponding methyl ketones. Thus, isopropanol, 2-butanol, 2-pentanol, and 2-hexanol were converted to acetone, 2-butanone, 2-pentanone, and 2-hexanone, respectively. Cell-free extracts derived from methanol-grown yeasts catalyzed an oxidized nicotinamide adenine dinucleotide-dependent oxidation of secondary alcohols to the corresponding methyl ketones, Primary alcohols were not oxidized. The effect of various environmental factors on the production of methyl ketones from secondary alcohols by methanol-grown Pichia sp. was investigated.     

Induction of Suppressed ADH Activity in Drosophila pachea Exposed to Different Alcohols

Laboratory-reared males of the cactophilic Drosophila pachea exhibit a spontaneous and sex-specific suppression of alcohol dehydrogenase (ADH) activity within 4 days after eclosion. A lack of ADH activity also is usually seen in wild-caught males, although relatively high activity is always seen in female flies. In the present study we examined the effectiveness of different alcohols and related compounds, including several found naturally in necroses of the host cactus, to induce suppressed ADH activity in wild males of D. pachea and to serve as enzyme substrates. The primary alcohols (methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol), and the secondary alcohols (2-propanol and 2-butanol), each induced activity after 24 h exposure, although to different degrees. 1,2-Propanediol was usually effective as an inducer, but 2,3-butanediol usually was ineffective. Little or no induction was seen with 1-octanol, 2-pentanol, 3-methyl-1-butanol, 3-hydroxy-2-butanone, or acetaldehyde. Although the compounds tested varied in their ability to function as ADH substrates, methanol was the only alcohol that showed no activity staining. Ethanol induction of ADH activity was apparent after 3-6 h exposure and induced activity decreased dramatically within 1 week of flies being placed in an alcohol-free environment. Ethanol exposure did not induce ADH in adult female D. pachea, or in adult males and females of D. acutilabella in which control males show reduced ADH activity compared to females. The implications of the loss of ADH activity in adult males of D. pachea, as they relate to feeding ecology and fitness, are discussed.     

Studies on the effect of alcohols on the chiral discrimination mechanisms of amylose stationary phase on the enantioseparation of nebivolol by HPLC

The chiral recognition mechanism of amylose CSPs has been described by achieving the enantiomeric resolution of (+/-)-nebivolol on Chiralpak AD and Chiralpak AD-RH columns with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol as mobile phases at different flow rates. The energies of interactions of methanol, ethanol, 1-propanol, 2-propanol and 1-butanol with both phases were calculated. The (+)-RRRS enantiomer eluted first when using methanol, ethanol and 1-propanol, while the elution order was reversed when using 2-propanol and 1-butanol as the mobile phases. It has been concluded that the reversal elution order observed was due in part to the chiral cavities on the amylose CSP which were responsible for the bondings of different magnitude between chiral stationary phase and enantiomers, which are influenced with the type of alcohol used as mobile phase on the conformation of the 3,5-dimethyl phenyl carbamate moiety on the pyranose ring system of the amylose.     

Biodiesel production from triolein and short chain alcohols through biocatalysis

Oleic acid alkyl esters (biodiesel) were synthesised by biocatalysis in solvent-free conditions. Different commercial immobilised lipases, namely Candida antarctica B, Rizhomucor miehei, and Pseudomonas cepacia, were tested towards the reaction between triolein and butanol to produce butyl oleate. Pseudomonas cepacia lipase resulted to be the most active enzyme reaching 100% of conversion after 6h. Different operative conditions such as reaction temperature, water activity, and reagent stoichiometric ratio were investigated and optimised. These conditions were then used to investigate the effect of linear and branched short chain alcohols. Methanol and 2-butanol were the worst alcohols: the former, probably, due to its low miscibility with the oil and the latter because secondary alcohols usually are less reactive than primary alcohols. Conversely, linear and branched primary alcohols with short alkyl chains (C(2)--C(4)) showed high reaction rate and conversion. A mixture of linear and branched short chain alcohols that mimics the residual of ethanol distillation (fusel oil) was successfully used for oleic acid ester synthesis. These compounds are important in biodiesel mixtures since they improve low temperature properties.     

13C-NMR and spectrophotometric studies of alcohol-lipid interactions

The interactions of butanol and mixtures of butanol and ethanol with dipalmitoylphosphatidyl choline (DPPC) liposomes have been investigated by both spectrophotometric measurements and Fourier transform 13C nuclear magnetic resonance spectroscopy. The spectrophotometric experiments indicate that butanol exhibits the same effects on the thermotropic properties of DPPC as the other short chain alcohols, methanol, ethanol and propanol, which have been shown to be characteristic of the alcohol induced transition of the lipid to the interdigitated state. An additive effect of butanol and ethanol on the induction of the interdigitated phase in DPPC was also observed. A decrease in line width and increase in T1 of the choline methyl signal were observed in the 13C-NMR experiments conducted at 32 degrees C when butanol was added to DPPC in increasing amounts suggesting an increase of disorder in the head group region of the lipid. Addition of ethanol to the NMR sample containing butanol produced hysteresis in the heating and cooling curves characteristic of the interdigitated state. In the interdigitated state, the choline methyl signal exhibited a T1 value equal to that when the lipid is in the fluid state. The increase of mobility in the head group region in the interdigitated gel state relative to the bilayer gel can be rationalized by the increase in surface area in that site when the lipid interdigitates.