Incorporation of pepsin within zwitterionic, anionic, and cationic lipid monolayers: A comparative study (original) (raw)
Related papers
Adsorption of pepsin in octadecylamine matrix at air–water interface
Biophysical Chemistry, 2010
The incorporation/entrapment of water-soluble surface-active enzyme, pepsin (PEP) within an insoluble cationic octadecylamine (ODA) monolayer is studied by Langmuir-Blodgett technique. The observation suggests that the incorporation of PEP is less preferable at compressed region (~30 mN/m). The electrostatic interaction plays a significant role for the greater incorporation of PEP in cationic ODA monolayer. The surface pressure-area isotherms along with FE-SEM analysis indicates the squeezing out of PEP from the monolayer at higher surface pressure. This will assist to select the optimum surface pressure to obtain a good quality and well-ordered Langmuir monolayer. FTIR study of amide bands together with FE-SEM imaging of ODA-PEP mixed film indicates that ODA perturbs the PEP by the increment of β-structure resulting into larger unfolding, intra, and intermolecular aggregates.
Lipid-protein interactions in monolayers
Chemistry and Physics of Lipids, 1982
We restricted ourselves to a few examples of the different methodological aspects of the investigation of lipid-protein interactions in monotayer assemblies. Experiments with monolayers have the unique advantage that the arrangement and packing of the molecules can be easily measured and controlled.
Journal of Colloid and Interface Science, 1999
The penetrant ability of the native glucose oxidase, GOx, and of the hydrophobically modified enzyme GO(mod) realized by grafting to its lysine residues alkyl C16 chains, into phosphatidylcholine dibehenoyl (DBPC), phosphatidylcholine dipalmitoyl (DPPC), phosphatidyl-ethanolamine dipalmitoyl (DPPE), phosphatidyl-serine dipalmitoyl (DPPS), and cholesterol (CHOL) monolayers was assessed by surface pressure measurements at constant area by enzyme injection to the aqueous phase beneath spread monolayers. As revealed by the magnitude of surface pressure increments (DeltaPi), both the quantities and the rates of penetration of the enzymes into these monolayers were lipid chemical nature and enzyme concentration dependent. When compared with GOx, GO(mod) displayed an enhanced penetrant ability into all the studied monolayers that resulted in rapidly attained DeltaPi plateau values, characteristic of stable systems. The influence of lipid hydrocarbon chain length and of the polar headgroup charge on the efficiency and effectiveness of GOx and GO(mod) penetration into these monolayers is discussed. Copyright 1999 Academic Press.
Journal of Colloid and Interface Science, 2007
In this communication we demonstrated the incorporation of water-soluble surface-active protein OVA within an insoluble cationic ODA monolayer and compared with zwitterionic (DPPC) and anionic (SA) monolayer. The incorporation of OVA is found to be more in ODA as compared to that of DPPC and SA. The kinetics of protein adsorption in lipid monolayer gives the idea that unfolding of OVA is less in case of DPPC than SA and ODA. The π-A isotherm and compressibility study gives the information about the different states of the protein-lipid mixed monolayer. At higher pressure, OVA tend to squeeze out from the lipids monolayer. High-resolution field emission scanning electron microscope (FE-SEM) images confirm this observation. The surface morphology of DPPC-OVA LB film is far better than ODA-OVA and SA-OVA LB film. OVA forms large irregular aggregates on SA and ODA monolayer. Fluorescence study reveals that protein structure is perturbed more in SA and ODA system compared to that of DPPC. The overall results indicate that DPPC monolayer is better to get protein lipid mixed film than SA and ODA monolayer.
Spontaneous formation of interfacial lipid-protein monolayers during adsorption from vesicles
Biophysical Journal, 1996
Spread and adsorbed monolayers of lipid-protein mixtures have served as models for biomembranes and pulmonary surfactant, but their similarity was unclear. Epifluorescence microscopy of monolayers spontaneously adsorbed from vesicles of dipalmitoylphosphatidylcholine or dipalmitoylphosphatidylcholine plus surfactant protein C (SP-C) showed gas, liquid expanded, and liquid condensed (LC) domains. The shapes and distribution of LC domains in the adsorbed and solvent-spread monolayers were quite similar. Labeled SP-C adsorbed into the air-water interface in the company of the lipids. In both forms of monolayers, SP-C occupied the fluid phase and reduced the size and amount of the LC domains. The properties suggest that these adsorbed and spread monolayers are analogous to one another.
Colloids and Surfaces B: Biointerfaces, 2013
The access to kinetic parameters of lipolytic enzyme adsorption onto lipids is essential for a better understanding of interfacial enzymology and lipase-lipid interactions. The interfacial adsorption of dog gastric lipase (DGL) was monitored as a function of pH and surface pressure (Π), independently from the catalytic activity, using non-hydrolysable 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) monomolecular films. The acid-stable DGL, which initiates fat digestion in the stomach, was then selected because its adsorption kinetics onto hydrophobic solid surfaces were already studied. This gastric lipase was therefore used as a model enzyme to validate both experimental and theoretical approaches. Results show that the adsorption process of DGL at the lipid/water interface depends on a pH-dependent adsorption equilibrium coefficient which is optimum at pH 5.0 (K Ads = 1.7 ±0.05 10 8 M -1 ). K Ads values further allowed an indirect estimation of the molar fraction (Φ E*(%) , mol%) as well as the molecular area (A E* ) of DGL adsorbed onto DLPC monolayer. Based on these data, a model for DGL adsorption onto DLPC monolayer at pH 5.0 is proposed for a surface pressure range of 15 to 25 mN m -1 .
Biophysical Journal, 2000
This study focuses on the structural organization of surfactant protein B (SP-B) containing lipid monolayers. The artificial system is composed of the saturated phospholipids dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) in a molar ratio of 4:1 with 0.2 mol% SP-B. The different "squeeze-out" structures of SP-B were visualized by scanning probe microscopy and compared with structures formed by SP-C. Particularly, the morphology and material properties of mixed monolayers containing 0.2 mol% SP-B in a wide pressure range of 10 to 54 mN/m were investigated revealing that filamentous domain boundaries occur at intermediate surface pressure (15-30 mN/m), while disc-like protrusions prevail at elevated pressure (50 -54 mN/m). In contrast, SP-C containing lipid monolayers exhibit large flat protrusions composed of stacked bilayers in the plateau region (app. 52 mN/m) of the pressure-area isotherm. By using different scanning probe techniques (lateral force microscopy, force modulation, phase imaging) it was shown that SP-B is dissolved in the liquid expanded rather than in the liquid condensed phase of the monolayer. Although artificial, the investigation of this system contributes to further understanding of the function of lung surfactant in the alveolus.
Enzymatic Modification of a Chemisorbed Lipid Monolayer †
Langmuir, 1996
The selectivity and specificity of enzymes may be exploited to create chemically complex surfaces which are difficult or impossible to achieve using classical synthetic chemistry. In this paper we discuss the preparation of a chemisorbed lipid film on a silicon wafer and explore the activity of free phospholipase C (PLC) on that film. A carboxylic acid derivative of the lipid dimyristoylphosphatidylcholine (DMPC) was attached to an amino-terminal silane (EDA) via amide bond formation to create an immobilized lipid layer (EDA-DMPC). Films were characterized using X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), atomic force microscopy (AFM), X-ray reflectivity, and ellipsometry. Following treatment with the enzyme phospholipase C (PLC), which catalyzes the cleavage of the lipid headgroup at the glycerol-phosphate ester bond, the lipid film was reanalyzed using the above techniques. Before analysis, nonspecifically adsorbed PLC was removed with a 25% trifluoroethanol rinse. XPS and SIMS results of the cleaned films show nearly complete removal of the phosphate from the lipid layer, indicating enzymatic activity of the PLC on the chemisorbed lipid layer.
Biophysical Journal, 2000
Epifluorescence microscopy combined with a surface balance was used to study monolayers of dipalmitoylphosphatidylcholine (DPPC)/egg phosphatidylglycerol (PG) (8:2, mol/mol) plus 17 wt % SP-B or SP-C spread on subphases containing SPA in the presence or absence of 5 mM Ca 2ϩ. Independently of the presence of Ca 2ϩ in the subphase, SPA at a bulk concentration of 0.68 g/ml adsorbed into the spread monolayers and caused an increase in the molecular areas in the films. Films of DPPC/PG formed on SPA solutions showed a pressure-dependent coexistence of liquid-condensed (LC) and liquid-expanded (LE) phases. Apart from these surface phases, a probe-excluding phase, likely enriched in SPA , was seen in the films between 7 mN/m Յ Յ 20 mN/m. In monolayers of SP-B/(DPPC/PG) spread on SPA , regardless of the presence of calcium ions, large clusters of a probe-excluding phase, different from probe-excluding lipid LC phase, appeared and segregated from the LE phase at near-zero surface pressures and coexisted with the conventional LE and LC phases up to ϳ35 mN/m. Varying the levels of either SPA or SP-B in films of SP-B/SP-A/(DPPC/PG) revealed that the formation of the probe-excluding clusters distinctive for the quaternary films was influenced by the two proteins. Concanavalin A in the subphase could not replace SPA in its ability to modulate the textures of films of SP-B/(DPPC/PG). In films of SP-C/SP-A/(DPPC/PG), in the absence of calcium, regions consisting of a probe-excluding phase, likely enriched in SPA , were detected at surface pressures between 2 mN/m and 20 mN/m in addition to the lipid LE and LC phases. Ca 2ϩ in the subphase appeared to disperse this phase into tiny probe-excluding particles, likely comprising Ca 2ϩ-aggregated SPA. Despite their strikingly different morphologies, the films of DPPC/PG that contained combinations of SP-B/SP-A or SP-C/SP-A displayed similar distributions of LC and LE phases with LC regions occupying a maximum of 20% of the total monolayer area. Combining SPA and SP-B reorganized the morphology of monolayers composed of DPPC and PG in a Ca 2ϩ-independent manner that led to the formation of a separate potentially protein-rich phase in the films.