Proton conduction measurement of KS.

A) Palladium hydride(PdHx) electrode behavior. Under a VSD, PdHx source split into Pd, H+, and e−. Protons are injected into the KS, whereas electrons travel through external circuitry and are measured. B) TLM geometry. Varying the distance between source and drain (LSD) distinguishes between the fixed PdHx−KS interface contact resistance and the varying bulk resistance. C) Optical image of TLM geometry with hydrated KS on the surface. Scale bar, 500μm. D) Transient response to a 1V bias in KS at 75%, 90%, 90% H2 RH, in which the current under 90% with hydrogen is much higher than that under 90% RH without hydrogen. E) Deuterium current (black) at 90% D2 humidity is lower than proton current (red). F) The normalized resistance RLN as a function of LSD, A linear fit gives a bulk material proton conductivity of 0.50 ± 0.11 mS cm-1.</p

Room-temperature proton conductivities of Nafion and known biopolymers.

Room-temperature proton conductivities of Nafion and known biopolymers.</p

The keratan sulfate.

(A) Chemical structure of KS. (B) An illustration of a three-monomer segment of KS. Possible intra- and inter-molecular hydrogen bonds as well as the hydrogen bonds between the water of hydration and the polar parts of the molecule form a continuous network comprised by hydrogen-bond chains. The sulfate group interacts with the hydrogen-bond network and forms an H3O+ (hydronium) ion.</p

Carbon-Binding Designer Proteins that Discriminate between sp²- and sp³‑Hybridized Carbon Surfaces

Robust and simple strategies to directly functionalize graphene- and diamond-based nanostructures with proteins are of considerable interest for biologically-driven manufacturing, biosensing, and bioimaging. Here, we identify a new set of carbon-binding peptides that vary in overall hydrophobicity and charge and engineer two of these sequences (Car9 and Car15) within the framework of <i>E. coli</i> thioredoxin 1 (TrxA). We develop purification schemes to recover the resulting TrxA derivatives in a soluble form and conduct a detailed analysis of the mechanisms that underpin the interaction of the fusion proteins with carbonaceous surfaces. Although equilibrium quartz crystal microbalance measurements show that TrxA::Car9 and TrxA::Car15 have similar affinities for sp²-hybridized graphitic carbon (<i>K</i>_d = 50 and 90 nM, respectively), only the latter protein is capable of dispersing carbon nanotubes. Further investigation by surface plasmon resonance and atomic force microscopy reveals that TrxA::Car15 interacts with sp²-bonded carbon through a combination of hydrophobic and π–π interactions but that TrxA::Car9 exhibits a cooperative mode of binding that relies on a combination of electrostatics and weaker π stacking. Consequently, we find that TrxA::Car9 binds equally well to sp²- and sp³-bonded (diamondlike) carbon particles whereas TrxA::Car15 is capable of discriminating between the two carbon allotropes. Our results emphasize the importance of understanding both bulk and molecular recognition events when exploiting the adhesive properties of solid-binding peptides and proteins in technological applications

Electronic control of H⁺ current in a bioprotonic device with carbon nanotube porins - Fig 2

(a) Pd contact with SLB. The SLB blocks H+ from transferring from the solution to the Pd contact even with V = -250 mV (vs. Ag/AgCl). (b) Pd contact with SLB incorporating 0.8 nm diameter CNTPs is semipermeable to H+, with CNTPs facilitating the rapid flow of H+ to the Pd/solution interface. (c) Upon addition of Ca+2 to the bulk solution, H+ current through CNTPs becomes partially blocked. (d) iH+ vs. time plots recorded at V = −250 mV and V = 20 mV. Blue trace: SLB, red trace: SLB with CNTPs, gray trace SLB with CNTPs in presence of Ca+2 ions in the bulk solution. (The data are collected from 3 different devices with different dimensions: Pd / SLB: 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs: 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs+Ca+2: 3 different devices of 2 × 50 μm. The error bars are the root mean square of the displacement of the data from the average value).</p

Conductive AFM of SLB with CNTPs channels.

(a) The current map for the Pd contact with SLB incorporating CNTPs. The hot spot (green spot) correspond to higher current (red trace) that represent CNT and the background (purple area) correspond to negligible amount of current (black trace) which represent SLB membrane. (b) In the IV curve the red trace collected from the green spot and the back trace collected from the purple area. The green spot has i ~ 1.78 nA ± 0.09 nA and purple area has i ~ 5.86 pA ± 0.98 pA. This current most likely represents the electron conductivity of CNT. (The data are collected from 3 different areas of the AFM image for both green spot and purple area. The error bars are the root mean square of the displacement of the data from the average value).</p

A bioprotonic device with integrated carbon nanotube porins (CNTPs) supports proton current across the SLB through the CNTPs when a negative voltage (<i>-V</i>) is applied on the Pd contact.

When H+ reach the surface of the Pd contact, they are reduced to H by an incoming electron and diffuse into the Pd to form palladium hydride (PdHx). The current density at the contact (–iH+), measures the rate of H+ flux along the CNTPs.</p

Electronic control of H⁺ current in a bioprotonic device with carbon nanotube porins - Fig 3

(a) Pd contact with SLB incorporating 0.8 nm diameter CNTPs with K-HEPES buffer at pH = 6.0, is semipermeable to H+, with CNTPs facilitating the rapid flow of H+ to the Pd/solution interface. (b) Pd contact with SLB incorporating Narrow CNTPs with K-HEPES buffer pH = 7.0, is still semipermeable to H+ but facilitating lower flow of H+ to the Pd/solution interface. (c) iH+ versus time plot for V = −250 mV and V = 50 mV. Gray trace SLB, red trace SLB+ CNTps (K-HEPES, pH = 6.0), black trace SLB+ CNTPs (K-HEPES, pH = 7.0). The iH+ for measurements K-HEPES pH = 6.0 is higher than K-HEPES pH = 7. We can hypothesize that at pH = 6.0 we have a driving force due to the lower pH across the membrane in addition to the applied voltage that expedite the flow of H+ while at pH = 7.0 we have only the applied voltage as a driving force to transport the H+ across. We did not observe any significant different between the iH+ at pH = 8.0 as compare to pH = 7.0 which might be due the buffer capacity of HEPES at different pH condition (Fig A in S1 File). (The data are collected from 3 different devices with different dimensions: SLB- K-HEPES pH = 7.0 : 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs+Ca+2: 3 different devices of 2 × 50 μm. The error bars are the root mean square of the displacement of the data from the average value).</p

Dendrimer Monolayers as Negative and Positive Tone Resists for Scanning Probe Lithography

A new scanning probe lithography scheme based on a self-assembled dendrimer monolayer on thin Ti films is presented. The method relies on the versatility of the functionalized dendrimer molecules to effectively function as etch resists by forming a densely packed self-assembled protective monolayer on a Ti film. Patterning of the Ti surface is accomplished using an AFM tip either as an ultra sharp scribe or as an electrical field point source to modify the monolayer. This, coupled to carefully selected etching conditions, allows the use of the dendrimer monolayers as both negative and positive tone resists. Facile formation of TiO2 features ca. 25 nm wide and 12 nm tall on silicon oxide and ca. 50 nm wide gaps in a thin Ti film can easily be achieved. The dendrimer resist approach can be further developed in order to improve the minimum feature size to the single dendrimer molecule level

A closer look at the ‘moment of disequilibrium’.

Two instances of disequilibrium characterized by (a) who is speaking, (b) hand position, and (c) body language. In (a) designer and scientist utterances/turn-taking are shown in a bar chart. In (b) hand positions are mapped, with higher numbers indicating closer proximity to the desk and graphic. Both (a) and (b) show the scientist withdrawing verbally and physically during disequilibrium. In (c) both scientists exhibit the discomfort of disequilibrium (clasped hands and crossed arms are known signals of stress).</p