Phase transition biopolymers and methods of use

Abstract

The present disclosure describes environmentally responsive polypeptides capable of displaying stimuli-triggered conformational changes in a reversible or irreversible manner that may be accompanied by aggregation. Polypeptides include a number of repeated motifs and may be elastomeric or non-elastomeric. The polypeptides may be used to deliver therapeutics to a biological site and to develop bioactive polypeptides that are environmentally responsive.

We claim: 
     
         1 . A environmentally responsive polypeptide comprising at least ten sequences selected from VGAPVG, LGAPVG, VPSALYGVG, VGPAVG, VTPAVG, VPSDDYGQG, VPSDDYGVG, TPVAVG, VPSTDYGVG, VPAGVG, VPTGVG, VPAGLG, VPHVG, VHPGVG, VPGAVG, VPGVAG, VRPVG, GRGDSPY, GRGDSPH, GRGDSPV, GRGDSPYG, RPLGYDS, RPAGYDS, RPXGYDS, GRGDSYP, GRGDSPYQ, GRGNSPYG, GRGDAPYQ, VPXSRNGG, VPHSRNGG, VPHSRNGL, VPGHSHRDFQPVLHLVALNSPL SGGMRG, HTHQDFQPVLHLVALNTPLSGGMRGIRPGG, FEWTPGWYQPYG or a combination thereof, wherein X is from zero to four amino acid residues, and wherein the polypeptide upon stimulation undergoes a conformational change that is accompanied by aggregation. 
     
     
         2 . The polypeptide of  claim 1 , wherein the at least ten sequences are consecutive. 
     
     
         3 . The polypeptide of  claim 1 , further comprising a spacer sequence between at least two of the at least ten sequences. 
     
     
         4 . The polypeptide of  claim 3 , wherein the spacer sequence comprises from one to twenty-six amino acids. 
     
     
         5 . The polypeptide of  claim 1 , wherein the polypeptide exhibits phase separation when exposed to a threshold temperature that is (i) above a lower critical solution temperature of the polypeptide, or (ii) below an upper critical solution temperature of the polypeptide, or exhibits phase separation when exposed to a threshold temperature that is above the lower critical solution temperature, and when exposed to a threshold temperature that is below the upper critical solution temperature. 
     
     
         6 . The polypeptide of  claim 5 , wherein the phase separation is reversible. 
     
     
         7 . The polypeptide of  claim 5 , wherein the phase separation is irreversible. 
     
     
         8 . The polypeptide of  claim 1 , wherein the polypeptide exhibits heat-irreversible phase separation when exposed to a threshold temperature that is above a lower critical solution temperature of the polypeptide, and exhibits reversible phase separation below the threshold temperature. 
     
     
         9 . The polypeptide of  claim 1 , wherein the polypeptide exhibits a reversible phase separation in response to a first stimulus. 
     
     
         10 . The polypeptide of  claim 9 , wherein the polypeptide exhibits an irreversible phase separation in response to a second different stimulus. 
     
     
         11 . The polypeptide of  claim 1 , wherein the at least 10 sequences convey LCST or UCST transition behavior, and wherein the polypeptide further comprises at least 9 sequences which are interspersed among the at least 10 sequences, wherein the at least 9 sequences convey LCST transition behavior when the at least 10 sequences convey UCST transition behavior, and UCST transition behavior when the at least 10 sequences convey LCST transition behavior, such that the polypeptide displays both LCST and UCST transition behavior. 
     
     
         12 . A fusion protein comprising the polypeptide of  claim 1 . 
     
     
         13 . A composition comprising the polypeptide of  claim 1 , conjugated to a molecule. 
     
     
         14 . The composition of  claim 13 , wherein the molecule is selected from an oligonucleotide, a therapeutic, a carbohydrate, a synthetic polymer, or a combination thereof. 
     
     
         15 . A polypeptide comprising the at least ten sequences of the polypeptide of  claim 1  as a reverse sequence when read from C-terminus to the N-terminus. 
     
     
         16 . A method of effecting a conformational change in a polypeptide comprising exposing the polypeptide of  claim 1  to a stimulus such that the polypeptide undergoes a conformational change that is accompanied by aggregation or solubilization in response to the stimulus. 
     
     
         17 . The method of  claim 16 , wherein the polypeptide becomes bioactive or loses bioactivity following the conformational change. 
     
     
         18 . A environmentally responsive polypeptide comprising at least ten PG motifs, and at least nine spacer sequences between the PG motifs, the at least nine spacer sequences being between five and thirty amino acid residues in length and not comprising a PG motif, and wherein the polypeptide upon stimulation undergoes a conformational change that is accompanied by aggregation.