Peptide networks

Abstract

Methods of modulating interfacial characteristics in a self-assembled, force-transmitting peptide network at a fluid-fluid interface are disclosed. The methods involve exposing a peptide capable of participating in a self-assembled, force-transmitting peptide network, either before or after it interacts with other peptides to form the peptide network to a stimulus that alters the chemical and/or physical properties of the peptide. Use of such methods in applications such as emulsions and foams are also disclosed.

1 . A method of modulating force transmission in a self-assembled, force-transmitting peptide network at a fluid-fluid interface, said method comprising exposing a peptide capable of participating in said network, either before or after it interacts with other peptides to form the peptide network, to a stimulus that alters the chemical and/or physical properties of the peptide, wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the stimulus is selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, a chaotropic agent, a salt, temperature or mixtures thereof; and   (iii) the peptide is an amphipathic peptide 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID Nos:6, 7, 8, 11 and 12, 
   (iv) the peptide has an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and   (v) the peptide is capable of interacting with other peptides at said interface depending on the physical and chemical state of the other peptides.   
     
     
         2 . A method according to  claim 1  wherein the stimulus results in the formation of a stable peptide network. 
     
     
         3 . A method according to  claim 1  wherein the stimulus results in the destabilization or dissipation of a peptide network. 
     
     
         4 . A method according to  claim 1  wherein the stimulus which alters the chemical and/or physical properties of the peptide alters at least one of:
 i) the ability of peptides within the peptide network to participate in intermolecular interactions, 
 ii) stabilization or destabilization of the conformation of a peptide within a network, 
 iii) increasing or reducing the affinity of a peptide for the fluid-fluid interface, or 
 iv) the rate of formation of the peptide network. 
 
     
     
         5 . A method according to  claim 1  wherein the stimulus which alters the chemical and/or physical properties of the peptide acts by removing a stimulus present or previously introduced into contact with the peptide network. 
     
     
         6 . A method of modulating force transmission in a self-assembled, force-transmitting peptide network at a fluid-fluid interface comprising the steps of:
 A) at a first time, exposing a peptide capable of participating in said peptide network, either before or after it interacts with other peptides to form the peptide network, to a first stimulus that alters the chemical and/or physical properties of the peptide; and   B) at a second time, exposing the peptide to a second stimulus that alters the chemical and/or physical properties of the peptide adopted upon exposure to the first stimulus;   
       wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m; 
 (ii) the first and second stimulus are independently selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, an oxidizing agent, a reducing agent, a chaotropic agent, a salt, temperature or mixtures thereof, and 
 (iii) the peptide is an amphipathic peptide 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID NOs:6, 7, 8, 11 and 12; 
 
 (iv) the peptide has an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and 
 (v) the peptide is capable of interacting with other peptides at said interface depending on the physical and chemical state of the other peptides. 
 
     
     
         7 . A method according to  claim 6  wherein the first stimulus causes formation or strengthening of a peptide network and the second stimulus causes a reduction in the strength or the dissipation of the peptide network formed or strengthened upon exposure to the first stimulus. 
     
     
         8 . A method according to  claim 6  wherein the first stimulus prevents the formation of or reduces the rate of formation of a peptide network and the second stimulus enhances formation of a peptide network at the fluid-fluid interface. 
     
     
         9 . A method according to  claim 6  wherein steps A) and/or B) are repeated one or more times. 
     
     
         10 . A method of modulating the formation of a peptide network at a fluid-fluid interface comprising exposing peptides capable of participating in a self-assembled, force-transmitting peptide network to a first condition or to a second condition, wherein under the first condition individual peptides have a first chemical and/or physical property that causes the peptides to interact with one another to thereby form the network and wherein under the second condition individual peptides have a second physical and/or chemical property that causes the peptides to separate thereby dissipating the network, wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the first and second condition are provided by addition of a stimulus selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, a chaotropic agent, a salt, temperature or mixtures thereof, and   (iii) the peptides are amphipathic peptides 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID Nos:6, 7, 8, 11 and 12; 
   (iv) the peptides have an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and   (v) the peptides are capable of interacting with other peptides at said interface depending on the physical and chemical state of the other peptides.   
     
     
         11 . A self-assembled, force-transmitting peptide network formed at a fluid-fluid interface wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the force transmission of the peptide network is manipulable by exposure to a stimulus which alters the physical and/or chemical properties of the peptide, wherein the stimulus is selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, a chaotropic agent, a salt, temperature or mixtures thereof; and   (iii) the peptide network comprises peptides which are amphipathic peptides 5 to 60 amino acid residues in length capable of forming an amphipathic α-helical secondary structure at the fluid-fluid interface having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5;   (iv) the peptides have an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character;   (v) and the peptides interact with one another at said interface.   
     
     
         12 . The self-assembled, force-transmitting peptide network according to  claim 11  wherein the peptides in the peptide network interact with one another by one or more of ion-pair interactions, dipole interactions, salt bridge formation, hydrogen bonding, short range solvation forces, hydrophobic interactions, osmotic attractive potential, metal ion bridging and surface charge interactions. 
     
     
         13 . The self-assembled, force-transmitting peptide network according to  claim 11  wherein the stimulus which alters the chemical and/or physical properties of the peptide alters at least one of
 i) the ability of peptides within the peptide network to participate in intermolecular interactions, 
 ii) stabilization or destabilization of the conformation of a peptide within a network, 
 iii) increasing or reducing the affinity of a peptide for the fluid-fluid interface, or 
 iv) the rate of formation of the peptide network. 
 
     
     
         14 . A foam comprising a self-assembled, force-transmitting peptide network formed at a fluid-fluid interface wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the force transmission of the peptide network is manipulable by exposure to a stimulus which alters the chemical and/or physical properties of the peptide, wherein the stimulus is selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, an oxidizing agent, a reducing agent, a chaotropic agent, a salt, temperature or mixtures thereof; and   (iii) the peptide network comprises peptides which are amphipathic peptides 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID Nos:6, 7, 8, 11 and 12; 
   (iv) the peptides have an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and   (v) the peptides interact with one another at said interface.   
     
     
         15 . An oil-in-water or water-in-oil emulsion comprising a self-assembled, force-transmitting peptide network formed at a fluid-fluid interface wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the force transmission of the peptide network is manipulable by exposure to a stimulus which alters the chemical and/or physical properties of the peptide, wherein the stimulus is selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, an oxidizing agent, a reducing agent, a chaotropic agent, a salt, temperature or mixtures thereof; and   (iii) the peptide network comprises peptides which are amphipathic peptides 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID Nos:6, 7, 8, 11 and 12; 
   (iv) the peptides have an affinity for the fluid-fluid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and   (v) the peptides interact with one another at said interface.   
     
     
         16 . A method of modulating the stability of a foam or emulsion comprising a self-assembled, force-transmitting peptide network at a liquid-gas or liquid-liquid interface respectively; said method comprising:
 A) at a first time, exposing the liquid-gas or liquid-liquid interface to a first stimulus that alters the chemical and/or physical properties of a peptide capable of forming a peptide network; and   B) at a second time, exposing the liquid-gas or liquid-liquid interface to a second stimulus that alters the chemical and/or physical properties of the peptide capable of forming a peptide network adopted upon exposure to the first stimulus,   
       wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m; 
 (ii) the first and second stimulus are independently selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, an oxidizing agent, a reducing agent, a chaotropic agent, a salt, temperature or mixtures thereof; and 
 (iii) the peptide is an amphipathic peptide 5 to 60 amino acid residues in length capable of forming at the fluid-fluid interface an ordered secondary structure selected from:
 (a) an amphipathic α-helix having the sequence (abcdefg)n or (gabcdef)n wherein residues a and d are hydrophobic amino acid residues, at least one of residues b, c, e, and g is an ionisable amino acid residue that may be modulated by protonation and deprotonation, residue f is a hydrophilic amino acid residue and n is an integer of 2 to 5; and 
 (b) a β-sheet having a hydrophobic face and a hydrophilic face selected from the group of SEQ ID Nos:6, 7, 8, 11 and 12; 
 
 (iv) the peptide has an affinity for the liquid-gas or liquid-liquid interface, wherein one phase of the interface possesses a hydrophobic character and the other phase possesses a hydrophilic character; and 
 (v) the peptide is capable of interacting with other peptides at said interface depending on the physical and chemical state of the other peptides. 
 
     
     
         17 . A method according to  claim 16  wherein the first stimulus allows formation of the peptide network, increases the rate of formation of the peptide network or increases force transmission of the peptide network and the second stimulus causes a reduction in force transmission of the peptide network or abolition of force transmission by the peptide network. 
     
     
         18 . A method according to  claim 17  wherein the second stimulus causes collapse of the foam or coalescence of the emulsion. 
     
     
         19 . A method according to  claim 16  wherein the first stimulus reduces the force transmission of the peptide network and the second stimulus increases the force transmission of the peptide network. 
     
     
         20 . A method according to  claim 16  wherein steps A) and/or B) are repeated one or more times. 
     
     
         21 . A peptide selected from the group consisting of: 
       
         
           
                 
                 
               
                   SEQ ID NO: 6 
                   Ac-PHFRFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 7 
                   Ac-PHFSFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 8 
                   Ac-PSFRFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 11 
                   Ac-PHFHFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 12 
                   Ac-PHFSFHFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 13 
                   Ac-MKQLADSLHQLAHKVSHLEHA-CONH 2 . 
                 
             
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         22 . A method of modulating force transmission in a self-assembled, force-transmitting peptide network at a fluid-fluid interface comprising exposing a peptide capable of participating in a self-assembled, force-transmitting peptide network, either before or after it interacts with other peptides to form the peptide network, to a stimulus that alters the chemical and/or physical properties of the peptide, wherein:
 (i) the force-transmitting peptide network has an interfacial elasticity modulus greater than or equal to 30 mN/m, and a maximum interfacial stress of greater than 0.5 mN/m;   (ii) the stimulus is selected from an acid, a base, a metal ion, a chelating agent, an organic or inorganic counterion, an oxidizing agent, a reducing agent, a chaotropic agent, a salt, temperature or mixtures thereof; and   (iii) the peptide capable of participating in a self-assembled, force-transmitting peptide network is selected from:   
       
         
           
                 
                 
               
                   SEQ ID NO: 2 
                   Ac-MKQLADSLHQLARQVSRLEHA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 3 
                   Ac-LMQLARQMKQLADSLMQLARQVSRLESA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 4 
                   Ac-MKELADSLMQLARQVDRLESA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 5 
                   Ac-MKQLADSLHQLAHQVSHLEHA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 6 
                   Ac-PHFRFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 7 
                   Ac-PHFSFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 8 
                   Ac-PSFRFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 9 
                   Ac-MEELADSLEELARQVEELESA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 10 
                   Ac-MKKLADSLKKLARQVKKLESA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 11 
                   Ac-PHFHFSFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 12 
                   Ac-PHFSFHFSP-CONH 2   
                 
                     
                 
                   SEQ ID NO: 13 
                   Ac-MKQLADSLHQLAHKVSHLEHA-CONH 2   
                 
                     
                 
                   SEQ ID NO: 14 
                   Ac-EISALEKEISALEKEISALEK-CONH 2   
                 
                     
                 
                   SEQ ID NO: 15 
                   Ac-KISALKEKISALKEKISALKE-CONH 2 .