caa a22 4500 47712724X CHVBK 20180405111653.0 cr unu---uuuuu 170330e19971001xx s 000 0 eng 10.1023/A:1012152117703 doi (NATIONALLICENCE)springer-10.1023/A:1012152117703 The Effect of β-Turn Structure on the Passive Diffusion of Peptides Across Caco-2 Cell Monolayers [Elektronische Daten] [Gregory Knipp, David Vander Velde, Teruna Siahaan, Ronald Borchardt] Purpose. To investigate the relationships between the β-turn structure of a peptide and its passive diffusion across Caco-2 cell monolayers, an in vitro model of the intestinal mucosa. Methods. Linear hydrophilic peptides (Ac-TyrProXaaZaaVal-NH2; Xaa = Gly, Ile and Zaa = Asp, Asn) and hydrophobic (Ac-YaaPro-XaaIleVal-NH2; Yaa = Tyr, Phe and Xaa = Gly, Ile: and Ac-PhePro-XaaIle-NH2; Xaa = Gly, He) peptides were synthesized and their effective permeability coefficients (Peff) were determined across Caco-2 cell monolayers. The lipophilicities of the peptides were estimated by measuring their partition coefficients (Po/w) between 1-octanol and HBSS. Two-dimensional NMR (2D-NMR) spectroscopy and circular dichroism (CD) spectroscopy was used to determine the solution structures of these model peptides. Results. Using 2D-NMR spectroscopy and CD spectroscopy, the hydrophilic Gly-containing peptides (Ac-TyrProGlyZaaVal-NH2; Zaa = Asp, Asn) were shown to exhibit a higher degree of β-turn structure in solution than the Ile-containing peptides (Ac-TyrProIleZaaVal-NH2; Zaa = Asp, Asn). CD spectroscopy was used to show that the Gly-containing hydrophobic peptides (Ac-YaaProGlyIleVal-NH2; Yaa = Tyr, Phe: and Ac-PheProGlyIle-NH2) exhibited a higher degree of β-turn structure in solution than the Ile-containing hydrophobic peptides. The Peff values of all four hydrophilic peptides across unperturbed Caco-2 cell monolayers were very low and no statistically significant differences were observed between the Gly- and Ile-containing penta-peptides within either the Asp or Asn series. The Peff values for the hydrophobic Gly-containing peptides were significantly greater than the Peff values determined for their Ile-containing counterparts. The Gly-containing penta- and tetrapeptides in the Phe series, which exhibited high permeation, were shown to be metabolically unstable. In contrast, the Gly- and Ile-containing pentapeptides in the Tyr series and the Ile-containing penta- and tetrapeptides in the Phe series, which exhibited low permeation, were metabolically stable. Conclusions. Hydrophobic peptides that exhibit significant β-turn structure in solution are more lipophilic as measured by log Po/w and more readily permeate Caco-2 cell monolayers via the transcellular route than hydrophobic peptides that lack this type of solution structure. The ability of these peptides to permeate Caco-2 cell monolayers via the transcellular route also exposed them to metabolism, presumably by cytosolic endopeptidases. Similar secondary structural features in hydrophilic peptides do not appear to sufficiently alter the physicochemical properties fo the peptides so as to alter their paracellular flux through unperturbed Caco-2 cell monolayers. Plenum Publishing Corporation, 1997 peptide delivery nationallicence paracellular diffusion nationallicence transcellular diffusion nationallicence solution conformation nationallicence Caco-2 cells nationallicence Knipp Gregory Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut Vander Velde David Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut Siahaan Teruna Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut Borchardt Ronald Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut Pharmaceutical Research Kluwer Academic Publishers-Plenum Publishers 14/10(1997-10-01), 1332-1340 0724-8741 14:10<1332 1997 14 11095 https://doi.org/10.1023/A:1012152117703 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1012152117703 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Knipp Gregory Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut NATIONALLICENCE 700 1- Vander Velde David Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut NATIONALLICENCE 700 1- Siahaan Teruna Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut NATIONALLICENCE 700 1- Borchardt Ronald Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., 66047, Lawrence, Kansas aut NATIONALLICENCE 773 0- Pharmaceutical Research Kluwer Academic Publishers-Plenum Publishers 14/10(1997-10-01), 1332-1340 0724-8741 14:10<1332 1997 14 11095 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer