bilayer vesicle (liposome). When real values of phospholipid molecule are
substituted, possibility of forming assemble structure is obtained.
2.4 Basic Structure of Biomembrane
Cell has various structures such as nucleus, mitochondria, endoplasmic reticulum,
lysosome, peroxisome, chloroplast (in plant cell), and plasma membrane in the case
of eukaryote. Primary function of biomembrane is compartmentation and selective
permeation for chemical reactions and metabolites. Major components of
biomembrane are proteins and lipids. Structure of biomembrane has been studied
by many researchers, and remarkable model was proposed by Singer and Nicolson
as ‘fluid mosaic membrane model’ in 1972 [2]. They have integrated several studies
from different viewpoints and their own experiment using electron microscopy.
Those studies are theory of hydrophobic effect of lipids in aqueous environment
[3], differential scanning calorimetric study of lipid dispersion [4], X-ray diffraction
study of cell membrane [5], Spin labeling study by ESR for lipid bilayer membrane
[6, 7], fluorescence microscopic study of antigens on a hybridized cell [8] and freezeetching electron microscopic study of lipid bilayer membrane [9–11]. For folded
structure of membrane proteins and even for soluble proteins, degree of hydrophobicity of each amino acid is important, and hydropathy index is useful to consider
structure and function of proteins (Fig. 2.3).
2.5 Proteins and Functions of a Cell
Most of functions in a cell are due to proteins, and major functions are catalytic
function of enzyme, signaling function of receptor and immune response of antibody. These functions are responsible for amino acid components of protein.
20 species of amino acids play their own role in the function of protein. Acidic
amino acid and basic amino acid are associated with electrophilic reaction and
nucleophilic reaction of catalytic function of enzyme, and hydrophobicity or hydrophilicity of amino acid is also important for formation of protein structure and
interaction with lipid bilayer membrane. Genetic information of amino acid
sequence in DNA is transferred to mRNA, and the protein is synthesized in ribosomal system. The genetic information is sufficient for formation of functional
structure of protein, and it is proved by an experiment using RNase A [12]. In the
experiment, RNase A was denatured by reductive treatment with 2-mercapto-thanol
2.5 Proteins and Functions of a Cell
23
substituted, possibility of forming assemble structure is obtained.
2.4 Basic Structure of Biomembrane
Cell has various structures such as nucleus, mitochondria, endoplasmic reticulum,
lysosome, peroxisome, chloroplast (in plant cell), and plasma membrane in the case
of eukaryote. Primary function of biomembrane is compartmentation and selective
permeation for chemical reactions and metabolites. Major components of
biomembrane are proteins and lipids. Structure of biomembrane has been studied
by many researchers, and remarkable model was proposed by Singer and Nicolson
as ‘fluid mosaic membrane model’ in 1972 [2]. They have integrated several studies
from different viewpoints and their own experiment using electron microscopy.
Those studies are theory of hydrophobic effect of lipids in aqueous environment
[3], differential scanning calorimetric study of lipid dispersion [4], X-ray diffraction
study of cell membrane [5], Spin labeling study by ESR for lipid bilayer membrane
[6, 7], fluorescence microscopic study of antigens on a hybridized cell [8] and freezeetching electron microscopic study of lipid bilayer membrane [9–11]. For folded
structure of membrane proteins and even for soluble proteins, degree of hydrophobicity of each amino acid is important, and hydropathy index is useful to consider
structure and function of proteins (Fig. 2.3).
2.5 Proteins and Functions of a Cell
Most of functions in a cell are due to proteins, and major functions are catalytic
function of enzyme, signaling function of receptor and immune response of antibody. These functions are responsible for amino acid components of protein.
20 species of amino acids play their own role in the function of protein. Acidic
amino acid and basic amino acid are associated with electrophilic reaction and
nucleophilic reaction of catalytic function of enzyme, and hydrophobicity or hydrophilicity of amino acid is also important for formation of protein structure and
interaction with lipid bilayer membrane. Genetic information of amino acid
sequence in DNA is transferred to mRNA, and the protein is synthesized in ribosomal system. The genetic information is sufficient for formation of functional
structure of protein, and it is proved by an experiment using RNase A [12]. In the
experiment, RNase A was denatured by reductive treatment with 2-mercapto-thanol
2.5 Proteins and Functions of a Cell
23