Formation of stable polypeptide monolayers at interfaces: controlling molecular conformation and orientation

Boncheva, Mila; Vogel, Horst

doi:10.1016/s0006-3495(97)78138-4

Cited by 110 publications

(95 citation statements)

References 56 publications

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“…Recent insight has been obtained from studies on peptides. Amphipathic helices adopt a preferential orientation parallel to the air-water interface (3). The ␣-helical content of ␤-casein-derived peptides increases on adsorption to a hydrophobic solid surface (4).…”

mentioning

confidence: 99%

Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association

Middelberg

Radke

Blanch

2000

Proc. Natl. Acad. Sci. U.S.A.

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We present a study of the adsorption of two peptides at the octane-water interface. The first peptide, Lac21, exists in mixed monomer-tetramer equilibrium in bulk solution with an appreciable monomer concentration. The second peptide, Lac28, exists as a tetramer in solution, with minimal exposed hydrophobic surface. A kinetic limitation to interfacial adsorption exists for Lac28 at moderate to high surface coverage that is not observed for Lac21. We estimate the potential energy barrier for Lac28 adsorption to be 42 kJ͞mol and show that this is comparable to the expected free energy barrier for tetramer dissociation. This finding suggests that, at moderate to high surface coverage, adsorption is kinetically limited by the availability of interfacially active monomeric ''domains'' in the subinterfacial region. We also show how the commonly used empirical equation for protein adsorption dynamics can be used to estimate the potential energy barrier for adsorption. Such an approach is shown to be consistent with a formal description of diffusion-adsorption, provided a large potential energy barrier exists. This work demonstrates that the dynamics of interfacial adsorption depend on protein thermodynamic stability, and hence structure, in a quantifiable way. P rotein adsorption at interfaces is a ubiquitous phenomenon of importance to diverse fields ranging from food processing to biomedical science. Consequently, research in this area has been widespread over the last century and a half, since Ascherson's observation regarding the formation of proteins skins around oil droplets in 1840 (1). Fundamental understanding of the processes involved in protein adsorption is, however, still lacking. Three key questions concern the protein structure at the interface, the adsorbed layer thickness, and the dynamics of protein adsorption.The first question is the subject of considerable research, particularly at the solid-liquid interface (2). Recent insight has been obtained from studies on peptides. Amphipathic helices adopt a preferential orientation parallel to the air-water interface (3). The ␣-helical content of ␤-casein-derived peptides increases on adsorption to a hydrophobic solid surface (4).The second question, regarding the thickness of surfaceadsorbed layers, has been addressed by using ellipsometry (5) and neutron reflectivity (6, 7). Surface pressure at the liquidliquid interface is dictated by the first layer of irreversibly adsorbed molecules, whereas subsequent layers may bind reversibly, causing an increase in thickness with no appreciable increase in surface pressure (5).The third question concerns the dynamics of protein adsorption and particularly how this is affected by protein structure and protein stability. Diffusion to the interface often controls the rate of protein adsorption and hence governs the interfacial tension at low surface coverage (8). At moderate to high coverage, an activation barrier to further adsorption has been observed for ␤-casein and lysozyme (8). The dynamic behavior in this regim...

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mentioning

confidence: 99%

Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association

Middelberg

Radke

Blanch

2000

Proc. Natl. Acad. Sci. U.S.A.

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“…In the normal helical structure of proteins, proline often causes a turn in the backbone. As an imino acid, it limits the rotation around the N-C␣ bond, resulting in a 15-20°kink in the helical structure (20,21). Thus, it is likely that the proline residues in the S4 putative ␣-helices of Ca 2ϩ channels introduce kinks to these ''moving ␣-helices.''…”

mentioning

confidence: 99%

Critical role of conserved proline residues in the transmembrane segment 4 voltage sensor function and in the gating of L-type calcium channels

Yamaguchi

Muth

Varadi

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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The fourth transmembrane segment (S4) has been shown to function as a voltage sensor in voltage-gated channels. On membrane depolarization, a stretch of S4 moves outward and initiates a number of conformational changes that ultimately lead to channel opening. Conserved proline residues are in the middle of the S4 of motifs I and III in voltage-dependent Ca 2؉ channels. Because proline often introduces a ''kink'' into a helical structure of proteins, these residues might have an intrinsic function in the voltage sensor. Voltage-dependent ion channels are thought to go through a series of conformational changes from nonconducting to conducting state on depolarization. Cloning and analysis of the predicted secondary structure of the Na ϩ channel (1), Ca 2ϩ channel (2), and the K ϩ channel (3) revealed a sharing of a common feature of positively charged transmembrane segments termed transmembrane segment 4 (S4). The S4 is likely to form an ␣-helix in which every third or fourth residue is basic (arginine or lysine) and carries positive charges. It is thought that the S4 ␣-helices traverse the membrane electric field and that, during depolarization, they move outward into the extracellular space and initiate conformational changes of the channel. This concept is supported by mutagenesis studies in which the mutations in charged residues (4-6) or uncharged residues (7-10) in S4 resulted in a shifted voltage dependence of activation. Several models have been proposed to account for the outward movement of S4, including a ''sliding helix'' (11) and a ''propagating helix'' (12). Direct proof for the outward movement of S4 has been shown in the Shaker K ϩ channel (13-15) as well as in the Na ϩ channel (16). Proline residues naturally occur in the middle of the S4 of motifs I and III in all known voltage-dependent Ca 2ϩ channel ␣ 1 subunits, including ␣ 1A, ␣ 1B, ␣ 1C, ␣ 1D, ␣ 1E, and ␣ 1S (17) and ␣ 1G and ␣ 1H (18,19). In the normal helical structure of proteins, proline often causes a turn in the backbone. As an imino acid, it limits the rotation around the N-C␣ bond, resulting in a 15-20°kink in the helical structure (20,21). Thus, it is likely that the proline residues in the S4 putative ␣-helices of Ca 2ϩ channels introduce kinks to these ''moving ␣-helices.'' The high conservation of these prolines among different Ca 2ϩ channels implies a critical importance in channel function. To clarify the role of these evolutionarily conserved prolines, we engineered and characterized mutant channels in which the prolines either were removed from motif IS4 and͞or motif IIIS4 or were added to equivalent positions in motif IIS4 and͞or IVS4 of the human-heart L-type Ca 2ϩ channel. Here, we describe crucial roles that S4 prolines play not only in voltage sensing but also in open-close transition of the channel. MATERIALS AND METHODSSite-Directed Mutagenesis and in Vitro Transcription. The human heart L-type Ca 2ϩ channel ␣ 1C subunit (22) cDNA was constructed in the plasmid pBluescript SK(ϩ) (Stratagene). Mutations were int...

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“…33 Finally, the peak present at 1667 cm -1 in the amide I region and the shoulder at around 1550 cm -1 (amide II region) reveal the presence of 310-helices in the bulk sample. 34,35 As shown in Fig. 3b, the amide I and II bands also clearly appear in the RAS spectrum of the Au(111) surface spin-coated with 1GBP, demonstrating the successful attachment of the polypeptides to the gold surface.…”

Section: Resultsmentioning

confidence: 69%

Single-Molecule Imaging of Gold-Binding Peptide Adsorbed on Au(111)

et al. 2013

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Formation of stable polypeptide monolayers at interfaces: controlling molecular conformation and orientation

Cited by 110 publications

References 56 publications

Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association

Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association

Critical role of conserved proline residues in the transmembrane segment 4 voltage sensor function and in the gating of L-type calcium channels

Single-Molecule Imaging of Gold-Binding Peptide Adsorbed on Au(111)

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