General. Solvents for extraction: ACS grade. Solvents for reaction: reagent grade. Reagents: unless otherwise noted, from Acros, Fluka, or Aldrich, highest quality available. TLC: silica gel 60 F 254 aluminum plates, (Whatman, type Al Sil G/UV, 250 µm layer); visualization by UV absorption) and/or by dipping in a soln. anisaldehyde/H 2 SO 4 /AcOH/EtOH 5:5:1:18) cerium(IV)sulfate (3 mM)/ammonium molybdate (250 mM) in aq. H 2 SO 4 (10%); followed by heating. Flash column chromatography (CC) was performed on silica gel 60 (0.40-0.63 mm, 230-440 mesh, EM Science) at low pressure (max. 2 bar). Melting points (uncorrected) MEL-TEMP II (Laboratory Devices Inc., USA). NMR: 1 H: δ values in ppm (TMS as internal standard); J [Hz], assignments of 1 H resonances were in some cases based on 2D experiments (1 H, 1 H-COSY); 13 C: δ values in ppm (TMS as internal standard); J [Hz]; assignments and multiplicities were based on 2D experiments (1 H, 13 C-COSY). ESI-MS (mode): m/z (intensity in %); performed with Micromat-LCT. Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was performed on a Voyager-Elite mass spectrometer (Perseptive Biosystems) with delayed extraction with THAP or DHB as the matrix with ammonium citrate added to the sample. Oligo-dipeptides were synthesized on an Expedite 8909 Nucleic Acid Synthesis system (Perseptive Biosystems) in the PNA mode with the following modifications: 0.14M dipeptide monomer in NMP/DMSO 4:1; 0.13M of HATU in NMP; washing soln. A: NMP/DMSO 4:1; washing soln. B: NMP/DMSO 4:1; deblocking soln. 30% piperidine in NMP/DMSO 4:1; capping: 5% Ac 2 O, 6% lutidine in NMP/DMSO 4:1; base-mixture: 0.14M DIPEA, 0.21M lutidine in NMP; coupling time of 30 min; in some cases double coupling step was used. Coupling efficiency was calculated by Fmoc-assay. For a majority of the synthesis, the average coupling efficiency was greater than 95%. HPLC purification of oligopeptides was achieved either by (a) ion-exchange: with MONO-Q HR 5/5 Pharmacia, 10 Ï 0.5 cm or Nucleogen-DEAE 60-7 Machery Nagel, 125 Ï 4, flow 1 ml / min; mobile phase: eluant A: 10 mM Na 2 HPO 4 , H 2 O, pH 11.5 (unless otherwise specified); eluant B: 10 mM Na 2 HPO 4 , 1 M NaCl, H 2 O, pH 11.5 (unless otherwise specified); or with Nucleogen-DEAE 60-7 Machery Nagel, 125 Ï 4, flow 1 ml / min, mobile phase: eluant A: 10 mM Na 2 HPO 4 , H 2 O, pH 7.0; eluant B: 10 mM Na 2 HPO 4 , 1 M NaCl, H 2 O, pH 7.0 or by (b) reverse-phase: Aquapore ODS 20 micron Brownlee, 250 Ï 10.0 mm, flow 4 ml / min. Mobile phase: eluant A: 0.1% TFA in H 2 O; eluant B: 0.1% TFA in MeCN. UV Spectra were recorded on a Cary 1 C