SUPPLEMENTARY INFORMATION. Low-molecular-weight gelators consisting of hybrid cyclobutane-based. peptides

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1 SUPPLEMENTARY INFORMATION Low-molecular-weight gelators consisting of hybrid cyclobutane-based peptides Sergi Celis, a Pau Nolis, b Ona Illa, a Vicenç Branchadell a and Rosa M. Ortuño* a a Departament de Química, Universitat Autònoma de Barcelona, 893 Cerdanyola del Vallès, Barcelona, Spain b Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, 893 Cerdanyola del Vallès, Barcelona, Spain CONTENTS Appearance of gels from compounds -4 S2 SEM micrographs of xerogels from compound in toluene at different concentrations IR data for -4 Computational calculations: alternative gelation pattern for NMR studies on gelation of tetrapeptide S3 S4 S5 S7 S

2 Appearance of the gels from compounds -4 ε Tetra Gly Pentane Toluene Et 2 O CHCl 3 EtOAc CH 2 Cl 2 THF iproh Acetone EtOH ACN MeOH H 2 O I I I Tetra 2 β Ala I I S I Tetra 3 GABA Tetra GABA 4 hexyl I I S I I I S S S I Fig. S Appearance of the gels formed from compounds - 4 in the different solvents tested. I = insoluble; S = soluble. S2

3 SEM micrographs of xerogels from compound in toluene at different concentrations 6 X augments 2 X augments 6 X augments 2 X augments, 7 mm (mgc) in toluene, 5 mm in toluene, 4 mm in toluene Fig. S2 SEM micrographs of xerogels from 7 mm (mgc), 5 mm,and 4mM peptide in toluene at two different magnifications each. S3

4 IR data Table S. N-H and C=O bands a in the IR spectra of peptides - 4 as solids, as xerogels from toluene, and in solution. NH CO Compound Crystalline c Xerogel Solution d Crystalline c Xerogel Solution d solid b solid b a In cm -. b ATR. c Xerogel from toluene gel at 3 mm in KBr. d 5 mm solution in CDCl 3 S4

5 Computational calculations: an alternative gelation pattern for An alternative interaction pattern has also been explored for dimeric (D ) and tetrameric (T ) aggregates of tetrapeptide. The resultant structures are shown in Figure S2. They are clearly unfavoured with respect to those shown in Figure 6 of the main text as can be deduced from comparison between data for D and T with data for D and T in Table S2. D T Fig. S2 Structures of dimeric (D ) and tetrameric (T ) aggregates of peptide optimized at the M6-2X/6-3G(d) level of calculation. Selected interatomic distances are in Å. S5

6 Table S2. Aggregation energies a computed for tetrapeptide In vacuo b In toluene c E E/n E E/n D (n=2) D (n=2). 5.6 T (n=4) T (n=4) a All values in kcal mol -. E corresponds to the n X (X) n process. b M6-2X/6-3G(d) level of calculation. c SMD-M6-2X/6-3+G(d,p)// M6-2X/6-3G(d) level of calculation. S6

7 NMR studies on gelation of tetrapeptide : Graphical representation of intensity and chemical-shift variations with temperature H7a/H7b pair: Normalized intensity,2,8,6,4 H7a H7b,2 5,25 5,2 5,5 5, H7a H7b 5,5 5, S7

8 H7 R /H7 S pair: Normalized intenstiy,2,8,6,4 H7R H7S,2 4, 4, 3,9 3,8 3,7 H7R 3,6 H7S 3,5 3,4 3,3 S8

9 H26 R /H26 S pair: Normalized intenstiy,2,8,6,4 H26R H26S,2 4,2 4, 4, 3,9 3,8 3,7 H26R H26S 3,6 3,5 S9

10 H2 and H: Normalized intenstiy,2,8,6,4 H2 H,2 4,8 4,75 4,7 4,65 4,6 H2 4,55 H 4,5 4,45 4,4 S

11 NH 9 : Normalized intenstiy,2,8,6,4 NH9,2 7, 6,95 6,9 6,85 6,8 NH9 6,75 6,7 6,65 Unfortunately, in this case, curve is broken due to overlapping with toluene signals S

12 NH 6 : Normalized intenstiy,2,8,6,4 NH6,2 7, 6,9 6,8 6,7 6,6 6,5 6,4 6,3 6,2 6, 6, NH6 S2

13 NH and NH 25 : Normalized intenstiy,2,8,6,4 NH25 NH,2 6,5 6,4 6,3 6,2 6, 6, 5,9 5,8 5,7 5,6 5,5 NH25 NH S3