Circular dic
hroism (CD) and Raman scattering were applied to t
he aqueous solution of minimalist LK peptidesconstructed wit
h successive KL repeats leading to t
he following generic primary sequence: (KL)
nK. T
hreepeptides of t
his family, a 3-mer (
n = 1), a 9-mer (
n = 4), and a 15-mer (
n = 7), are analyzed in t
his report.Raman spectra of t
he 3-mer (KLK, a random c
hain) and its labile-
hydrogen deuterated species yield a set ofinteresting information for analyzing longer peptides of t
his series. Alt
houg
h t
he CD spectrum of t
he 9-mer(KLKLKLKLK) reveals a signal traditionally assigned to a random structure, t
he corresponding Ramanspectrum allows finding a mixture of conformations in solution, adopting predominantly
hars/beta2.gif" BORDER=0 ALIGN="middle">-type structures.T
his fact proves t
he utility of Raman spectroscopy to eliminate eventual ambiguity concerning conformationalassignments in peptides based only on t
he use of CD tec
hnique. Finally, t
he 15-mer (KLKLKLKLKLKLKLK)gives rise to CD and Raman spectra clearly assignable to a
hars/beta2.gif" BORDER=0 ALIGN="middle">-type structure. On t
he basis of all t
he observedresults on t
he 15-mer, we can confirm t
hat t
his peptide may exist as isolated
hars/beta2.gif" BORDER=0 ALIGN="middle">-strands at low concentration(sub-micromolar), flat-oriented at t
he air/water interface, w
hereas at
hig
h concentrations (millimolar), non-H-bonded immersible aggregates mig
ht be formed. A
hypot
hetical model for t
hese
hars/beta2.gif" BORDER=0 ALIGN="middle">-strand aggregates couldbe proposed as stabilized by an interior
hydrop
hobic core and a
hydrop
hilic external face, formed by leucineand lysine side c
hains, respectively.