Robust platform for inline Raman monitoring and control of perfusion cell culture.

Perfusion cell culture has been gaining increasing popularity for biologics manufacturing due to benefits such as smaller footprint, increased productivity, consistent product quality and manufacturing flexibility, cost savings, and so forth. Process Analytics Technologies tools are highly desirable for effective monitoring and control of long-running perfusion processes. Raman has been widely investigated for monitoring and control of traditional fed batch cell culture process. However, implementation of Raman for perfusion cell culture has been very limited mainly due to challenges with high-cell density and long running times during perfusion which cause extremely high fluorescence interference to Raman spectra and consequently it is exceedingly difficult to develop robust chemometrics models. In this work, a platform based on Raman measurement of permeate has been proposed for effective analysis of perfusion process. It has been demonstrated that this platform can effectively circumvent the fluorescence interference issue while providing rich and timely information about perfusion dynamics to enable efficient process monitoring and robust bioreactor feed control. With the highly consistent spectral data from cell-free sample matrix, development of chemometrics models can be greatly facilitated. Based on this platform, Raman models have been developed for good measurement of several analytes including glucose, lactate, glutamine, glutamate, and permeate titer. Performance of Raman models developed this way has been systematically evaluated and the models have shown good robustness against changes in perfusion scale and variations in permeate flowrate; thus models developed from small lab scale can be directly transferred for implementation in much larger scale of perfusion. With demonstrated robustness, this platform provides a reliable approach for automated glucose feed control in perfusion bioreactors. Glucose model developed from small lab scale has been successfully implemented for automated continuous glucose feed control of perfusion cell culture at much larger scale.

Pseudomonas orientalis F9 Pyoverdine, Safracin, and Phenazine Mutants Remain Effective Antagonists against Erwinia amylovora in Apple Flowers.

The recently characterized strain Pseudomonas orientalis F9, an isolate from apple flowers in a Swiss orchard, exhibits antagonistic traits against phytopathogens. At high colonization densities, it exhibits phytotoxicity against apple flowers. P. orientalis F9 harbors biosynthesis genes for the siderophore pyoverdine as well as for the antibiotics safracin and phenazine. To elucidate the role of the three compounds in biocontrol, we screened a large random knockout library of P. orientalis F9 strains for lack of pyoverdine production or in vitro antagonism. Transposon mutants that lacked the ability for fluorescence carried transposons in pyoverdine production genes. Mutants unable to antagonize Erwinia amylovora in an in vitro double-layer assay carried transposon insertions in the safracin gene cluster. As no phenazine transposon mutant could be identified using the chosen selection criteria, we constructed a site-directed deletion mutant. Pyoverdine-, safracin-, and phenazine mutants were tested for their abilities to counteract the fire blight pathogen Erwinia amylovoraex vivo on apple flowers or the soilborne pathogen Pythium ultimumin vivo in a soil microcosm. In contrast to some in vitro assays, ex vivo and in vivo assays did not reveal significant differences between parental and mutant strains in their antagonistic activities. This suggests that, ex vivo and in vivo, other factors, such as competition for resources or space, are more important than the tested antibiotics or pyoverdine for successful antagonism of P. orientalis F9 against phytopathogens in the performed assays.IMPORTANCEPseudomonas orientalis F9 is an antagonist of the economically important phytopathogen Erwinia amylovora, the causal agent of fire blight in pomme fruit. On King's B medium, P. orientalis F9 produces a pyoverdine siderophore and the antibiotic safracin. P. orientalis F9 transposon mutants lacking these factors fail to antagonize E. amylovora, depending on the in vitro assay. On isolated flowers and in soil microcosms, however, pyoverdine, safracin, and phenazine mutants control phytopathogens as clearly as their parental strains.

Fe2+ chelator proferrorosamine A: a gene cluster of Erwinia rhapontici P45 involved in its synthesis and its impact on growth of Erwinia amylovora CFBP1430.

Proferrorosamine A (proFRA) is an iron (Fe2+) chelator produced by the opportunistic plant pathogen Erwinia rhapontici P45. To identify genes involved in proFRA synthesis, transposon mutagenesis was performed. The identified 9.3 kb gene cluster, comprising seven genes, designated rosA-rosG, encodes proteins that are involved in proFRA synthesis. Based on gene homologies, a biosynthetic pathway model for proFRA is proposed. To obtain a better understanding of the effect of proFRA on non-proFRA producing bacteria, E. rhapontici P45 was co-cultured with Erwinia amylovora CFBP1430, a fire-blight-causing plant pathogen. E. rhapontici P45, but not corresponding proFRA-negative mutants, led to a pink coloration of E. amylovora CFBP1430 colonies on King's B agar, indicating accumulation of the proFRA-iron complex ferrorosamine, and growth inhibition in vitro. By saturating proFRA-containing extracts with Fe2+, the inhibitory effect was neutralized, suggesting that the iron-chelating capability of proFRA is responsible for the growth inhibition of E. amylovora CFBP1430.

Atomically precise bottom-up fabrication of graphene nanoribbons.

Graphene nanoribbons-narrow and straight-edged stripes of graphene, or single-layer graphite-are predicted to exhibit electronic properties that make them attractive for the fabrication of nanoscale electronic devices. In particular, although the two-dimensional parent material graphene exhibits semimetallic behaviour, quantum confinement and edge effects should render all graphene nanoribbons with widths smaller than 10 nm semiconducting. But exploring the potential of graphene nanoribbons is hampered by their limited availability: although they have been made using chemical, sonochemical and lithographic methods as well as through the unzipping of carbon nanotubes, the reliable production of graphene nanoribbons smaller than 10 nm with chemical precision remains a significant challenge. Here we report a simple method for the production of atomically precise graphene nanoribbons of different topologies and widths, which uses surface-assisted coupling of molecular precursors into linear polyphenylenes and their subsequent cyclodehydrogenation. The topology, width and edge periphery of the graphene nanoribbon products are defined by the structure of the precursor monomers, which can be designed to give access to a wide range of different graphene nanoribbons. We expect that our bottom-up approach to the atomically precise fabrication of graphene nanoribbons will finally enable detailed experimental investigations of the properties of this exciting class of materials. It should even provide a route to graphene nanoribbon structures with engineered chemical and electronic properties, including the theoretically predicted intraribbon quantum dots, superlattice structures and magnetic devices based on specific graphene nanoribbon edge states.

Face-to-face panel meetings versus remote evaluation of fellowship applications: simulation study at the Swiss National Science Foundation.

OBJECTIVES: To trial a simplified, time and cost-saving method for remote evaluation of fellowship applications and compare this with existing panel review processes by analysing concordance between funding decisions, and the use of a lottery-based decision method for proposals of similar quality. DESIGN: The study involved 134 junior fellowship proposals for postdoctoral research ('Postdoc.Mobility'). The official method used two panel reviewers who independently scored the application, followed by triage and discussion of selected applications in a panel. Very competitive/uncompetitive proposals were directly funded/rejected without discussion. The simplified procedure used the scores of the two panel members, with or without the score of an additional, third expert. Both methods could further use a lottery to decide on applications of similar quality close to the funding threshold. The same funding rate was applied, and the agreement between the two methods analysed. SETTING: Swiss National Science Foundation (SNSF). PARTICIPANTS: Postdoc.Mobility panel reviewers and additional expert reviewers. PRIMARY OUTCOME MEASURE: Per cent agreement between the simplified and official evaluation method with 95% CIs. RESULTS: The simplified procedure based on three reviews agreed in 80.6% (95% CI: 73.9% to 87.3%) of applicants with the official funding outcome. The agreement was 86.6% (95% CI: 80.6% to 91.8%) when using the two reviews of the panel members. The agreement between the two methods was lower for the group of applications discussed in the panel (64.2% and 73.1%, respectively), and higher for directly funded/rejected applications (range: 96.7%-100%). The lottery was used in 8 (6.0%) of 134 applications (official method), 19 (14.2%) applications (simplified, three reviewers) and 23 (17.2%) applications (simplified, two reviewers). With the simplified procedure, evaluation costs could have been halved and 31 hours of meeting time saved for the two 2019 calls. CONCLUSION: Agreement between the two methods was high. The simplified procedure could represent a viable evaluation method for the Postdoc.Mobility early career instrument at the SNSF.

Randomised, quadruple blinded, placebo controlled, multicentre trial investigating prophylactic tamsulosin in prevention of postoperative urinary retention in men after endoscopic total extraperitoneal inguinal hernia repair (STOP-POUR trial): a study protocol.

INTRODUCTION: Postoperative urinary retention (POUR) is a common complication after inguinal hernia repair with a reported incidence up to 34%. It can be described as the inability to initiate urination or insufficient bladder emptying following surgery. It usually requires the use of catheterisation to empty the bladder in order to prevent further injury to the bladder or kidneys and to relief from pain. Tamsulosin is a medication that is commonly used in men with urinary symptoms related to an enlarged prostate. There is some evidence to suggest that it may also potentially be beneficial for preventing POUR. METHODS AND ANALYSIS: This is a multicentre, blinded, prospective, phase IV randomised controlled trial with parallel allocation. Six hundred and thirty-four patients scheduled for elective endoscopic inguinal hernia repair surgery will be recruited. There will be effective (concealed) randomisation of the subjects to the intervention/control groups. Group assignment will be performed using a covariate-adaptive allocation procedure to provide a balance for selected covariates. The interventional group receives 0.4 mg tamsulosin hydrochloride and the control-group receives one placebo capsule matching the active study drug, both daily, starting from 5 days prior to the day of surgery, at the day of surgery and for 1 day following surgery. The primary outcome is any need for urinary catheterisation postoperatively as a binary outcome. Secondary outcome measures include postoperative pain, change in International Prostate Symptom Score from baseline prior to surgery to after surgery and hospital stay. ETHICS AND DISSEMINATION: The study has been approved by the Northwestern and Central Switzerland Ethics Committee (2020-00569) and it is being conducted in accordance with the Declaration of Helsinki and Good Clinical Practice. Study results will be disseminated through peer-reviewed journals and national and international scientific conferences. TRIAL REGISTRATION NUMBERS: SNCTP000003904. NCT04491526.

Furan hydrogenation over Pt(111) and Pt(100) single-crystal surfaces and Pt nanoparticles from 1 to 7 nm: a kinetic and sum frequency generation vibrational spectroscopy study.

Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to systematically study the adsorption and hydrogenation of furan over Pt(111) and Pt(100) single-crystal surfaces and size-controlled 1.0-nm, 3.5-nm and 7.0-nm Pt nanoparticles at Torr pressures (10 Torr of furan, 100 Torr of H(2)) to form dihydrofuran, tetrahydrofuran, and the ring-cracking products butanol and propylene. As determined by SFG, the furan ring lies parallel to all Pt surfaces studied under hydrogenation conditions. Upright THF and the oxametallacycle intermediate are observed over the nanoparticle catalysts under reaction conditions. Butoxy increases in surface concentration over Pt(111) with increasing temperature in agreement with selectivity trends.

Two-dimensional polymer formation on surfaces: insight into the roles of precursor mobility and reactivity.

We report on a combined scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) study on the surface-assisted assembly of the hexaiodo-substituted macrocycle cyclohexa-m-phenylene (CHP) toward covalently bonded polyphenylene networks on Cu(111), Au(111), and Ag(111) surfaces. STM and XPS indicate room temperature dehalogenation of CHP on either surface, leading to surface-stabilized CHP radicals (CHPRs) and coadsorbed iodine. Subsequent covalent intermolecular bond formation between CHPRs is thermally activated and is found to proceed at different temperatures on the three coinage metals. The resulting polyphenylene networks differ significantly in morphology on the three substrates: On Cu, the networks are dominated by "open" branched structures, on the Au surface a mixture of branched and small domains of compact network clusters are observed, and highly ordered and dense polyphenylene networks form on the Ag surface. Ab initio DFT calculations allow one to elucidate the diffusion and coupling mechanisms of CHPRs on the Cu(111) and Ag(111) surfaces. On Cu, the energy barrier for diffusion is significantly higher than the one for covalent intermolecular bond formation, whereas on Ag the reverse relation holds. By using a Monte Carlo simulation, we show that different balances between diffusion and intermolecular coupling determine the observed branched and compact polyphenylene networks on the Cu and Ag surface, respectively, demonstrating that the choice of the substrate plays a crucial role in the formation of two-dimensional polymers.

Porous graphene as an atmospheric nanofilter.

The fabrication of nanoscale membranes exhibiting high selectivity is an emerging field of research. The possibility to use bottom-up approaches to fabricate a filter with porous graphene and analyze its functionality with first principle calculations is investigated. Here, the porous network is produced by self-assembly of the hexaiodo-substituted macrocycle cyclohexa-m-phenylene (CHP). The resulting porous network exhibits an extremely high selectivity in favor of H(2) and He among other atmospheric gases, such as Ne, O(2), N(2), CO, CO(2), NH(3), and Ar. The presented membrane is superior to traditional filters using polymers or silica and could have great potential for further technological applications such as gas sensors or fuel cells.

Hydrogenation of the alpha,beta-unsaturated aldehydes acrolein, crotonaldehyde, and prenal over Pt single crystals: a kinetic and sum-frequency generation vibrational spectroscopy study.

Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three alpha,beta-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr of aldehyde, 100 Torr of hydrogen) in the temperature range of 295-415 K. SFG-VS data showed that acrolein has mixed adsorption species of eta(2)-di-sigma(CC)-trans, eta(2)-di-sigma(CC)-cis as well as highly coordinated eta(3) or eta(4) species. Crotonaldehyde adsorbed to Pt(111) as eta(2) surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the eta(2) adsorption species and became more highly coordinated as the temperature was raised to 415 K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation "cracking" product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotyl alcohol.

Pseudomonas orientalis F9: A Potent Antagonist against Phytopathogens with Phytotoxic Effect in the Apple Flower.

In light of public concerns over the use of pesticides and antibiotics in plant protection and the subsequent selection for spread of resistant bacteria in the environment, it is inevitable to broaden our knowledge about viable alternatives, such as natural antagonists and their mode of action. The genus Pseudomonas is known for its metabolic versatility and genetic plasticity, encompassing pathogens as well as antagonists. We characterized strain Pseudomonas orientalis F9, an isolate from apple flowers in a Swiss orchard, and determined its antagonistic activity against several phytopathogenic bacteria, in particular Erwinia amylovora, the causal agent of fire blight. P. orientalis F9 displayed antagonistic activity against a broad suite of phytopathogenic bacteria in the in vitro tests. The promising results from this analysis led to an ex vivo assay with E. amylovora CFBP1430Rif and P. orientalis F9 infected detached apple flowers. F9 diminished the fire blight pathogen in the flowers but also revealed phytotoxic traits. The experimental results were discussed in light of the complete genome sequence of F9, which revealed the strain to carry phenazine genes. Phenazines are known to contribute to antagonistic activity of bacterial strains against soil pathogens. When tested in the cress assay with Pythium ultimum as pathogen, F9 showed results comparable to the known antagonist P. protegens CHA0.

Probing enantiospecific interactions between proline and an l-glutathione self-assembled monolayer by modulation excitation ATR-IR spectroscopy.

The interaction of proline with self-assembled monolayers (SAMs) of l-glutathione (gamma-glu-cys-gly) on gold was investigated by a combination of attenuated total reflection (ATR-IR) infrared and modulation excitation spectroscopy (MES). The latter technique makes use of phase-sensitive detection of periodically varying signals and allows discrimination between species with different kinetics such as dissolved proline and adsorbed molecules. By applying a convection-diffusion model coupled to adsorption and desorption, it was possible to extract relative adsorption and desorption rates from the experimental data for the two enantiomers of proline, fully accounting for mass transport within the flow-through cell. The results show that, in particular, the desorption kinetics is different for the two enantiomers. Therefore, the l-glutathione SAM can discriminate between enantiomers, d-proline being stronger bound. The IR spectra reveal that upon interaction with proline the adsorbed l-glutathione is protonated at the gly part of the molecule, which, in the absence of proline, is bound to the gold surface as carboxylate. The observed protonation of adsorbed l-glutathione upon interaction with proline goes along with a structural change of the former, which seems to play an important role for enantiodiscrimination.

Adsorption kinetics, orientation, and self-assembling of N-acetyl-L-cysteine on gold: a combined ATR-IR, PM-IRRAS, and QCM study.

The adsorption of N-acetyl-L-cysteine from ethanol solution on gold has been studied by in situ attenuated total reflection infrared (ATR-IR) spectroscopy, polarization modulation infrared reflection absorption spectroscopy, and a quartz crystal microbalance. After an initial fast adsorption, in situ ATR-IR revealed two considerably slower processes, besides further adsorption. The appearance of carboxylate bands and the partial disappearance of the carboxylic acid bands demonstrated that part of the molecules on the surface underwent deprotonation. In addition, the C=O stretching vibration of the carboxylic acid group shifted to lower and the amide II band to higher wavenumbers, indicating hydrogen-bonding interactions within the adsorbate layer. Based on the initial ATR-IR spectrum, which did not reveal deprotonation, the orientation of the molecule within the adsorbate layer was determined. For this, density functional theory was used to calculate the transition dipole moment vectors of the vibrational modes of N-acetyl-l-cysteine. The projections of the latter onto the z-axis of the fixed surface coordinate system were used to determine relative band intensities for different orientations of the molecule. The analysis revealed that the amide group is tilted with respect to and points away from the surface, whereas the carboxylic acid is in proximity to the surface, which is also supported by a shift of the C-O-H bending mode. This position of the acid group favors its deprotonation assisted by the gold surface and easily enables intermolecular interactions. Periodic acid stimuli revealed reversible protonation/deprotonation of part of the adsorbed molecules. However, only non-hydrogen-bonded carboxylic acid groups showed a response toward the acid stimuli.

Does the Earth's magnetic field serve as a reference for alignment of the honeybee Waggle dance?

The honeybee (Apis mellifera) waggle dance, which is performed inside the hive by forager bees, informs hive mates about a potent food source, and recruits them to its location. It consists of a repeated figure-8 pattern: two oppositely directed turns interspersed by a short straight segment, the "waggle run". The waggle run consists of a single stride emphasized by lateral waggling motions of the abdomen. Directional information pointing to a food source relative to the sun's azimuth is encoded in the angle between the waggle run line and a reference line, which is generally thought to be established by gravity. Yet, there is tantalizing evidence that the local (ambient) geomagnetic field (LGMF) could play a role. We tested the effect of the LGMF on the recruitment success of forager bees by placing observation hives inside large Helmholtz coils, and then either reducing the LGMF to 2% or shifting its apparent declination. Neither of these treatments reduced the number of nest mates that waggle dancing forager bees recruited to a feeding station located 200 m north of the hive. These results indicate that the LGMF does not act as the reference for the alignment of waggle-dancing bees.

Surface-supported 2D heterotriangulene polymers.

We report on the assembly of tribromo-substituted dimethylmethylene-bridged triphenylamine (heterotriangulene) on Ag(111). Depending on activation temperature, two-dimensional porous metal-coordination or covalent networks are obtained.

Porous graphenes: two-dimensional polymer synthesis with atomic precision.

We demonstrate, by surface-assisted coupling of specifically designed molecular building blocks, the fabrication of regular two-dimensional polyphenylene networks with single-atom wide pores and sub-nanometer periodicity.

Probing chiral interfaces by infrared spectroscopic methods.

Biological homochirality on earth and its tremendous consequences for pharmaceutical science and technology has led to an ever increasing interest in the selective production, the resolution and the detection of enantiomers of a chiral compound. Chiral surfaces and interfaces that can distinguish between enantiomers play a key role in this respect as enantioselective catalysts as well as for separation purposes. Despite the impressive progress in these areas in the last decade, molecular-level understanding of the interactions that are at the origin of enantiodiscrimination are lagging behind due to the lack of powerful experimental techniques to spot these interactions selectively with high sensitivity. In this article, techniques based on infrared spectroscopy are highlighted that are able to selectively target the chiral properties of interfaces. In particular, these methods are the combination of Attenuated Total Reflection InfraRed (ATR-IR) with Modulation Excitation Spectroscopy (MES) to probe enantiodiscriminating interactions at chiral solid-liquid interfaces and Vibrational Circular Dichroism (VCD), which is used to probe the structure of chirally-modified metal nanoparticles. The former technique aims at suppressing signals arising from non-selective interactions, which may completely hide the signals of interest due to enantiodiscriminating interactions. Recently, this method was successfully applied to investigate enantiodiscrimination at self-assembled monolayers of chiral thiols on gold surfaces. The nanometer size analogues of the latter--gold nanoparticles protected by a monolayer of a chiral thiol--are amenable to VCD spectroscopy. It is shown that this technique yields detailed structural information on the adsorption mode and the conformation of the adsorbed thiol. This may also turn out to be useful to clarify how chirality can be bestowed onto the metal core itself and the nature of the chirality of the latter, which is manifested in the metal-based circular dichroism activity of these nanoparticles.

D-penicillamine adsorption on gold: an in situ ATR-IR spectroscopic and QCM study.

The adsorption of penicillamine from ethanol on gold was studied in situ by attenuated total reflection infrared (ATR-IR) and quartz crystal microbalance (QCM) experiments. Both ATR-IR and QCM reveal a fast mass uptake. In ethanol, the molecule adopts a zwitterionic form. Upon adsorption, part of the molecules deprotonate at the amine group, which is a relatively slow process that goes along with a strong shift of the nu(as)(COO(-)) mode. Both ATR-IR and QCM confirm a physisorbed layer. ATR-IR furthermore shows that the latter consists of zwitterionic molecules only, whereas both zwitterionic and anionic species are found in the chemisorbed layer. The infrared spectra of the physisorbed and chemisorbed layers are rather different, and the molecules within both layers seem to be oriented with respect to the surface. The ATR-IR spectra furthermore indicate that all three functional groups of penicillamine (i.e., thiol, carboxylate, and amine) interact with the surface, and density functional theory calculations support this finding. QCM also shows that the molecule uses considerably more space on the surface than molecules of similar size, which supports a three-point interaction. The latter leads to a strong anchoring of the molecule to the metal, which may explain the exceptional capability of penicillamine to bind metals.

Enantiodiscrimination between an N-acetyl-L-cysteine SAM and proline: an in situ spectroscopic and computational study.

A combination of attenuated total reflection infrared (ATR-IR) and modulation excitation spectroscopy (MES) is used to study the enantiodiscriminating interactions between proline and a chiral, self-assembled monolayer (SAM) of N-acetyl-L-cysteine on gold. The N-acetyl-L-cysteine SAM consists of a mixture of protonated and deprotonated molecules. Whereas both species are influenced by adsorbed proline, only the deprotonated molecules are involved in enantiodiscrimination. Density functional theory (DFT) calculations reveal that electrostatics dominates the interaction between the two molecules. By modulating the absolute configuration of proline over the chiral SAM, and a subsequent phase-sensitive detection of the periodically varying signals in the ATR-IR spectra, the small spectral differences between the diastereomeric complexes are spotted. The resulting difference spectrum is in qualitative agreement with the spectrum predicted by the DFT calculations.

Adsorption kinetics of L-glutathione on gold and structural changes during self-assembly: an in situ ATR-IR and QCM study.

The adsorption of L-glutathione (gamma-Glu-Cys-Gly) from ethanol on gold surfaces was studied in situ by both attenuated total reflection infrared (ATR-IR) spectroscopy and using a quartz crystal microbalance (QCM). The molecule is firmly anchored to the gold surface through the thiol group. Different IR signals of adsorbed L-glutathione, notably the amide I and nu(-COOH), show significantly different behavior with time, which reveals that their increase is not related to adsorption (mass uptake) alone. This indicates that structural transformations take place during the formation of the self-assembled monolayer (SAM). In particular, the intensity of the acid signal increases quickly only within the first couple of minutes. The complexity of the self-assembling process is confirmed by QCM measurements, which show fast mass uptake within about 100 s followed by a considerably slower regime. The structural change superimposed on the mass uptake is, based on the in situ time-resolved ATR-IR measurements, assigned to the interaction of the acid group of the Gly moiety with the surface. The latter group is protonated in ethanol but deprotonates upon interaction with the gold surface. The protonation-deprotonation equilibrium is sensitive to external stimuli, such as the presence of dissolved L-glutathione molecules. The interaction of the acid group with the surface and concomitant deprotonation proceeds via two distinguishable steps, the first being a reorientation of the molecule, followed by the deprotonation.