Infrared Characterization of Different Water Types inside Reverse Micelles

Boicelli, C. A.; Giomini, Marcello; Giuliani, Anna Maria

doi:10.1366/0003702844555115

Cited by 39 publications

(16 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Typical ν 1,3 (OH) bands of gradually hydrated DODPC are displayed in Figure . The band shapes obtained in the L α and gel states are very similar and resemble the typical structure of the ν 1,3 (OH) band of fully or partially hydrated PC lipids in the fluid state. − The broad feature consists of subbands assigned to the symmetric and antisymmetric stretching vibration of free, i.e., non-hydrogen-bound, OH groups (3615 cm -1 ) and of hydrogen-bound OH-groups (<3615 cm -1 ) and to the Fermi resonance (3280 cm -1 ) at 2ν 2 (OH), where ν 2 (OH) ≈ 1650 cm -1 is the H 2 O bending vibration . In general, the ν 1,3 (OH) bandwidth reflects the distribution of hydrogen bonds of variable strength among a variety of binding sites.…”

Section: Resultssupporting

confidence: 53%

See 1 more Smart Citation

Hydration-Induced Gel States of the Dienic Lipid 1,2-Bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine and Their Characterization Using Infrared Spectroscopy

et al. 1997

View full text Add to dashboard Cite

The lyotropic phase behavior of the dienic lipid 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine (DODPC) has been investigated by means of IR spectroscopy at 25 °C. Gradual hydration has been realized exposing the lipid to an atmosphere of variable relative humidity (RH). Upon scans of decreasing RH, the liquid crystalline lipid undergoes the chain-freezing transition to a metastable gel state. By storage of the sample at low RH, the gel transforms to a crystalline subgel designated as SGI. Subsequent hydration induces the conversion to a second subgel (SGII). The subgel phases are characterized by the dense packing of the acyl chains as indicated by the correlation field splitting of the CH2 rocking and bending modes. Band shifts of phosphate group vibrations as well as the splitting of the carbonyl stretching mode are correlated with the hydration of the polar region of the bilayer given in terms of the molar ratio of water to lipid. The ν1,3(OH) absorption band of water yields qualitative information about the water−lipid interaction. The drastic sharpening of this band in the SGI phase was attributed to the reduction of water binding sites on the lipid, leading to a more uniform population of water molecules adsorbed onto the lipid headgroup. The external conditions of phase transformation of DODPC were compared with corresponding data of dimyristoylphosphatidylcholine (DMPC) having the same number of subsequent methylene segments in the acyl chains. Apparent differences can be attributed to the influence of the diene groups representing a rigid spacer inserted between the methylene chains and the ester groups of the lipid, i.e., in a position near the polar/apolar interface of the bilayer.

show abstract

Section: Resultssupporting

confidence: 53%

“…parts a and c of Figure ). It represents an approximate measure of the amount of water bound to the lipid 31,46,47 regardless of slight variations of the extinction coefficients of the water fractions differing in their H-bond characteristics 6 Number of water molecules per lipid, R WL (a), wavenumbers at half-maximum absorbance (cf.…”

Section: Resultsmentioning

confidence: 99%

Hydration-Induced Gel States of the Dienic Lipid 1,2-Bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine and Their Characterization Using Infrared Spectroscopy

et al. 1997

View full text Add to dashboard Cite

show abstract

“…Further hydration, even past the percolation threshold, results in the aqueous environment becoming progressively more bulklike in nature. While there is evidence for the existence of three water types in the spherical nonorganogel forming lecithin/benzene reverse micelles, studies of lecithin/cyclohexane reverse micelles detect only two types, strongly bound and free. In contrast, by accounting for solvated monomers, Maitra et al find that for micelles between w 0 = 4.8 to 6.8, the hydration range we have studied, half the water population is bound and the other half free.…”

Section: Discussionmentioning

confidence: 99%

“…The first water type is considered to be strongly bound to the surfactant headgroup, while the final type is considered to be bulklike. Although results vary, several studies have found the existence of three water types in various reverse micellar systems. , …”

Section: Introductionmentioning

confidence: 99%

Dynamics of Polar Solvation in Lecithin/Water/Cyclohexane Reverse Micelles

1998

View full text Add to dashboard Cite

The solvation dynamics of water in lecithin/cyclohexane reverse micelles have been determined via ultrafast time-resolved fluorescence studies. At hydration levels w 0 ≤ 4.8, the reverse micellar samples are nonviscous. Here a single relaxation time is observed that is much longer than the response of free or bulk water. In contrast, small additions of water to the samples produces a viscous gel, referred to by others as an organogel or “living polymer”. At hydration levels of w 0 ≥ 5.8, three relaxation times are observed with approximate time constants of 0.5, 15, and 200 ps, the shortest of which correlates to free water motion. The dynamics reveal no evidence of micelle crossover or branch points associated with gel formation. In comparison to Aerosol OT reverse micelles of similar hydration, the water in the lecithin reverse micelles is significantly more restricted. It is proposed that lecithin sequesters significantly more water than previously predicted precluding formation of distinct core water pools in the micelles. The results are also compared to models for aqueous structure and dynamics near phospholipid membranes and to bulk water dynamics.

show abstract

“…Water molecules in bulk state form hydrogen bonds in tetrahedral arrangements that are constantly breaking and forming, and this dynamical structure can be disrupted when it is confined in small cavities , or at interfaces. , The properties of highly structured water are different from those of water in the bulk. In reverse aggregates of surfactants, water may be found as bound water and/or as free water. ,− Primary bound water is interacting directly with the polar heads of the surfactants and forms the first hydration shell; secondary bound water is next to primary hydration shell and is bound less tightly; free water is present in stabilized water pools and resembles bulk water, although the dynamics of the entrapped water in the aggregates may be slower. The nature of the hydrophilic segments also affects the polarity of entrapped water.…”

Section: Introductionmentioning

confidence: 99%

Water-Induced Phase Transition in Cyclohexane/n-Hexanol/Triton X-100 Mixtures at a Molar Composition of 1/16/74 Studied by NMR

et al. 2017

View full text Add to dashboard Cite

Molecular aggregation in a mixture of Triton X-100/n-hexanol/cyclohexane at a molar ratio of 1/16/74 is studied upon addition of small amounts of water. The composition of organic components has been chosen at a ratio n-hexanol/cyclohexane where a well-formed hydrogen bond network has been described. The ratio Triton X-100/n-hexanol has been chosen to afford a stoichiometry of ethylene oxide (EO) residues/n-hexanol of 1/2. At these conditions the addition of water consecutively produces the appearance of three defined phases: a clear solution, a lamellar phase, and a microemulsion. The two corresponding transitions occur at water/EO/n-hexanol molar ratios of 2/1/2 (clear to lamella), and 3/1/2 (lamella to microemulsion), while phase separation occurs at a molar ratio of 4/1/2, highlighting the important role of stoichiometry. Molecular dynamics measured by H NMR techniques, such as DOSY, and calculations of T and T relaxation times allow distinguishing the transition between the different phases and justifying their structure. Molecular assembly in the three phases is organized around hydrogen bond networks in which the hydroxyl groups of both TX-100 and n-hexanol, ethylene oxide groups of TX-100, and water participate. 1D H NMR spectral changes correlate with the different characteristics of the different phases. As the main characteristics of the lamellar phase we find a very restricted mobility of the molecules involved, and water chemical shifts in 1DH NMR spectra of around 5.0 ppm, higher than that of bulk water appearing at 4.7 ppm.

show abstract

Infrared Characterization of Different Water Types inside Reverse Micelles

Cited by 39 publications

References 9 publications

Hydration-Induced Gel States of the Dienic Lipid 1,2-Bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine and Their Characterization Using Infrared Spectroscopy

Hydration-Induced Gel States of the Dienic Lipid 1,2-Bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine and Their Characterization Using Infrared Spectroscopy

Dynamics of Polar Solvation in Lecithin/Water/Cyclohexane Reverse Micelles

Water-Induced Phase Transition in Cyclohexane/n-Hexanol/Triton X-100 Mixtures at a Molar Composition of 1/16/74 Studied by NMR

Contact Info

Product

Resources

About