Molecularly Resolved Images of Peptide-Functionalized Gold Surfaces by Scanning Tunneling Microscopy

Abstract

Peptide-terminated monolayers were formed through a Huisgen cycloaddition reaction between an α-helical peptide containing two propargylglycine unnatural functional groups 20 Å apart and an alkanethiol self-assembled monolayer (SAM) on a gold surface containing 25% surface density of reactive azide terminal groups. The azide- and peptide-terminated surfaces were imaged by scanning tunneling microscopy (STM) using a low tunneling current of 10 pA. On the peptide-terminated surface, oblong features ~30 Å long and ~20 Å wide were observed and attributed to individual surface-bound α-helical peptides oriented parallel to the gold surface. These features covered an area of the surface corresponding to a density of 0.11 ± 0.01 peptides nm(-2), compared with a theoretical density of ~0.14 peptides nm(-2) for a fully reacted surface. Finally, no evidence of peptide aggregation was observed on either short (<10 nm) or long (~100 nm) length scales.

Peptide flatlandia: a new-concept peptide for positioning of electroactive probes in proximity to a metal surface

“…18,19 In particular, it is well-known that sequences containing both C α -tetrasubstituted and C α -trisubstituted α-amino acids promote the formation of 3 10 -helical structures for peptides shorter than 7-8 units, while a conformational transition to α-helical structures arises in longer sequences. 20,21 The inclusion of one Adt residue every three amino acids in a short peptide rich in C αtetrasubstituted residues should locate the dithiolane side chains in the correct positions to anchor the peptide chain cooperatively to the gold surface. We therefore synthesized a hexapeptide, denoted as Fc-CO-6Adt2, formed by two Adt-Ala-Aib triads and functionalized with an electroactive ferrocenoyl (Fc) group at the N-terminus (Scheme 1).…”

Surface bound VEGF mimicking peptide maintains endothelial cell proliferation in the absence of soluble VEGFin vitro

“…This value falls within the range of densities reported elsewhere on various substrates, ranging from femto [44][45][46] to picomoles per mm 2 . 29,[47][48][49] We then found that the EO 7 -SVV surface had a significant impact on HUVEC adhesion and proliferation. We also found that this effect was specifically due to the presence of SVVYGLR since surfaces presenting the bioactive RGD peptide performed significantly less well than EO 7 -SVV surfaces.…”

“…Using complementary surface analysis techniques we were able to quantify the surface density of SVVYLGR which stands at 1.6 ± 0.2 pmol per mm 2 . This value falls within the range of densities reported elsewhere on various substrates, ranging from femto to picomoles per mm 2 …”

Beneficial Effect of Covalently Grafted α-MSH on Endothelial Release of Inflammatory Mediators for Applications in Implantable Devices

“…Numerous reports confirm the effective modification of the gold substrate with peptides but little to no information is given on the quantitative evaluation of surface density [ 56 – 58 ]. In contrast, when quantifying surface density is possible using STM on atomically smooth gold, it is difficult to implement this type of substrate for biological experiments [ 59 ]. Others were able to quantify the interparticle distance of large dendrimers on gold by AFM [ 60 ] but since RGD clustering is known to strongly impact cell adhesion[ 61 ], the technique described by Lagunas et al .…”