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Badania FTIR-ATR i fluorescencyjne układów białkowo-lipidowych

Litwińczuk-Mammadova A., Cieślik-Boczula K., Rospenk M.

Wiadomości Chemiczne

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2017

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[Z] 71, 1-2

109--132

EN

Lipid-protein systems paly curtail roles in living systems [49]. Hence, a determination of their structure at different levels of organization is still one of the most important tasks in many research projects. A study of lipid-protein systems is based on many physicochemical techniques, such as spectroscopy of FTIR, Raman, fluorescence, NMR, EPR, as well as DLS, DSC and TEM methods. In the presented paper tow of the most frequently used methods, that is FTIR and fluorescence spectroscopy, will be discussed in details. They are characterized by a relatively low cost of sample preparation, a short measuring time, and they give a huge number of structural and physicochemical information about lipid-protein systems. In the FTIR-ATR spectroscopy many of vibrational bands are commonly used as very precise vibrational indicators of structural changes in lipids and proteins (Fig. 1) [1–6]. They allows to characterize lipid and protein components separately in mixed systems. Additionally, structural changes in lipid membranes can be monitored in one FTIR-ATR experiment simultaneously in a region of hydrophilic lipid head-groups (Fig. 5) [17, 18], in a hydrophobic part composed of hydrocarbon lipid chains (see Figures 2 and 3) [7–9], and in a lipid membrane interface represented by ester lipid groups (Fig. 4) [4, 6, 11, 12]. A secondary structure of proteins and peptides in different experimental conditions can be defined in the FTIR-ATR spectroscopy on the base of amide I bands (Fig. 6 and Tabs 1, 2 and 3) [20–22]. A fluorescence spectroscopy is a complementary methods to FTIR spectroscopy in a study of lipid-protein systems. It competes information about time-dependent and very fast (in a scale of femtoseconds) structural processes in both lipids [41–45] and proteins [23, 27, 48]. The folding, denaturation, and aggregation of proteins and lipid membranes accompanied by changes in an order, packing and hydration of the system under study [23, 27, 41–45, 48].

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Budowa i funkcje układów białkowo-lipidowych

Litwińczuk-Mammadova A., Cieślik-Boczula K., Rospenk M.

Wiadomości Chemiczne

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2016

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[Z] 70, 11-12

723--746

EN

Biomembranes play many structural and functional roles in both prokaryotic and eukaryotic cells [10]. They define compartments, the communication between the inside and outside of the cell. The main components of biomembranes are lipids and proteins, which form protein-lipid bilayer systems [10]. A structure and physicochemical properties of protein-lipid membranes, which determines biological activities of biomembranes, are strongly dependent on interactions between lipid and protein components and external agents such as a temperature, pH, and a membrane hydration [4]. A lipid bilayer matrix serves as a perfect environment for membrane proteins (Fig. 1), and it assures activities of these proteins. Because biomembranes are composed of many different groups of lipids and proteins and have a complex structure, it is difficult to study in details their physicochemical properties using physicochemical methods. For these reason, lipid membranes of liposomes are used in many scientific laboratories for studding processes associated with a lipid phase transition, a membrane hydration, or protein-membrane interactions. The structure of liposomes (Fig. 5), and an influence of pH and an ionic strength on a lipid bilayer structure are discussed in the presented work. The role of membrane proteins in determination of biological activities of biomembranes is highlighted. A high variety of a structure and an enzymatic activity of membrane proteins is responsible for a high diversity of biological functions of cell membranes [2]. α-Lactalbumin (α-LA) is a peripheral membrane protein (Figs 8 and 9), its biological function is strongly related to its conformational structure and interaction with lipid membranes [49]. The complex of α-LA in a molten globule conformational state with oleic acid, termed as a HAMLET complex, are disused in a context of its anti-tumor activity.

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Characterization of the Structure of PDP-DPPC Bilayers by DFT and PM3 Calculations

Cieślik-Boczula K., Koll A.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

1081-1093

EN

The character of 3-pentadecylphenol (PDP)-dipalmitoylophosphatidylcholine (DPPC) interactions in a bilayer system was investigated using DFT and semi-empirical calculations. The obtained results were supported by ATR-IR spectra. The strongest intermolecular hydrogen bond was found between the phenolic OH and the PO2 groups of the DPPC molecule. The presence of water and hydrocarbon chains slightly weakens the strength of this PDP-DPPC interaction. In contrast to a pureDPPC bilayer, thewater molecules do not destroy the H-bonds formed by PO2 moieties and even enhance the total energy of the interaction. Both the van derWaals’interactions in the hydrophobic core of the PDP-DPPC aggregate and the intermolecular H-bond in the hydrophilic part make this complex more rigid, which influences its physical and chemical properties.