TY - JOUR
T1 - Hydrogelation Induced by Change in Hydrophobicity of Amino Acid Side Chain in Fmoc-Functionalised Amino Acid
T2 - Significance of Sulfur on Hydrogelation
AU - Reddy, Samala Murali Mohan
AU - Dorishetty, Pramod
AU - Deshpande, Abhijit P.
AU - Shanmugam, Ganesh
N1 - Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PY - 2016/7/18
Y1 - 2016/7/18
N2 - Although a few Fmoc-functionalised amino acids (Fmoc-AA) are capable of forming hydrogels, the exact levels of hydrophobicity, hydrogen bonding, and ionic nature of the Fmoc-AA gelator required for hydrogel formation remains uncertain. Here, the role of hydrophobicity of amino acid side chain, particularly in the formation of hydrogel, was studied by using Fmoc-norleucine (Fmoc-Nle) and its simple sulfur analogues such as Fmoc-methionine (Fmoc-M) in which the γCH2 of Fmoc-Nle is replaced by sulfur. Results indicate that Fmoc-M forms thermally reversible hydrogels in water (pH ca. 6.8), whereas Fmoc-Nle fails to display any gelation under similar conditions. The result suggests that substitution of the sulfur atom likely reduces the hydrophobicity of the alkyl side chain in Fmoc-Nle to the optimum level, which is sufficient to induce supramolecular hydrogelation in Fmoc-M. The difference in the self-association behaviour of Fmoc-M and Fmoc-Nle emphasise the importance of weak noncovalent interaction between side chains (in addition to the hydrogen-bond and aromatic interactions) to stabilise supramolecular self-assembly of Fmoc-functionalised compounds. The current observations provide a lead to the design of new sulfur-based low molecular weight gelators for various potential applications.
AB - Although a few Fmoc-functionalised amino acids (Fmoc-AA) are capable of forming hydrogels, the exact levels of hydrophobicity, hydrogen bonding, and ionic nature of the Fmoc-AA gelator required for hydrogel formation remains uncertain. Here, the role of hydrophobicity of amino acid side chain, particularly in the formation of hydrogel, was studied by using Fmoc-norleucine (Fmoc-Nle) and its simple sulfur analogues such as Fmoc-methionine (Fmoc-M) in which the γCH2 of Fmoc-Nle is replaced by sulfur. Results indicate that Fmoc-M forms thermally reversible hydrogels in water (pH ca. 6.8), whereas Fmoc-Nle fails to display any gelation under similar conditions. The result suggests that substitution of the sulfur atom likely reduces the hydrophobicity of the alkyl side chain in Fmoc-Nle to the optimum level, which is sufficient to induce supramolecular hydrogelation in Fmoc-M. The difference in the self-association behaviour of Fmoc-M and Fmoc-Nle emphasise the importance of weak noncovalent interaction between side chains (in addition to the hydrogen-bond and aromatic interactions) to stabilise supramolecular self-assembly of Fmoc-functionalised compounds. The current observations provide a lead to the design of new sulfur-based low molecular weight gelators for various potential applications.
KW - amino acids
KW - gels
KW - mechanical properties
KW - self-assembly
KW - sulfur
UR - http://www.scopus.com/inward/record.url?scp=84979266053&partnerID=8YFLogxK
U2 - 10.1002/cphc.201600132
DO - 10.1002/cphc.201600132
M3 - Article
C2 - 27017582
AN - SCOPUS:84979266053
SN - 1439-4235
VL - 17
SP - 2170
EP - 2180
JO - ChemPhysChem
JF - ChemPhysChem
IS - 14
ER -