Electrochemical and thermal detection of allergenic substance lysozyme with molecularly imprinted nanoparticles.

Lysozyme (LYZ) is a small cationic protein which is widely used for medical treatment and in the food industry to act as an anti-bacterial agent; however, it can trigger allergic reactions. In this study, high-affinity molecularly imprinted nanoparticles (nanoMIPs) were synthesized for LYZ using a solid-phase approach. The produced nanoMIPs were electrografted to screen-printed electrodes (SPEs), disposable electrodes with high commercial potential, to enable electrochemical and thermal sensing. Electrochemical impedance spectroscopy (EIS) facilitated fast measurement (5-10 min) and is able to determine trace levels of LYZ (pM) and can discriminate between LYZ and structurally similar proteins (bovine serum albumin, troponin-I). In tandem, thermal analysis was conducted with the heat transfer method (HTM), which is based on monitoring the heat transfer resistance at the solid-liquid interface of the functionalized SPE. HTM as detection technique guaranteed trace-level (fM) detection of LYZ but needed longer analysis time compared to EIS measurement (30 min vs 5-10 min). Considering the versatility of the nanoMIPs which can be adapted to virtually any target of interest, these low-cost point-of-care sensors hold great potential to improve food safety.

Assessment of air pollution tolerance potential of selected dicot tree species for urban forestry.

Air pollution is one of the killers of our age especially for the urban areas. Urban forestry which involves planting more trees has been considered as one of the prominent strategies to mitigate air pollution. Identification of trees tolerant to air pollution is important for plantation drives being organized across the country. The present study aimed to compare the air pollution tolerance potential of 46 tree species growing in Guru Nanak Dev University (GNDU) campus, Amritsar, using two indices, viz., Air Pollution Tolerance Index (APTI) and Anticipated Performance Index (API). APTI is based on four biochemical parameters, viz., relative water content, leaf extract pH, total chlorophyll, and ascorbic acid contents of leaf samples, whereas API takes into consideration morphological and socioeconomic values of plant species along with their APTI. Based on APTI values calculated for 46 tree species, only 2 tree species, viz., Psidium guajava (46.26) and Cassia fistula (41.83), were found to be tolerant to air pollution, while 25 species showed intermediate tolerance. API scores revealed one tree species, namely, P. guajava, as an excellent performer, 8 species as very good performers, and 28 species as moderate to good performers against air pollution. In conclusion, tree species like Alstonia scholaris, C. fistula, Ficus tsjakela, Grevillea robusta, Kigelia africana, Mangifera indica, Melia azedarach, P. guajava, Pongamia pinnata, Pterospermum acerifolium, Putranjiva roxburghii, Syzygium cumini, Terminalia arjuna, and Toona ciliata can be considered as most desirable for plantations in areas around GNDU campus.

Role of horizontally transferred copper resistance genes in Staphylococcus aureus and Listeria monocytogenes.

Bacteria have evolved mechanisms which enable them to control intracellular concentrations of metals. In the case of transition metals, such as copper, iron and zinc, bacteria must ensure enough is available as a cofactor for enzymes whilst at the same time preventing the accumulation of excess concentrations, which can be toxic. Interestingly, metal homeostasis and resistance systems have been found to play important roles in virulence. This review will discuss the copper homeostasis and resistance systems in Staphylococcus aureus and Listeria monocytogenes and the implications that acquisition of additional copper resistance genes may have in these pathogens.

Spatiotemporal assessment of potentially toxic elements in sediments and roadside soil samples and associated ecological risk in Ropar wetland and its environs.

Sediments from banks of the Sutlej River and roadside soils from vicinity of Ropar wetland (collected during pre- and post-monsoon seasons, 2013) were analysed to determine the spatiotemporal distribution of potentially toxic elements (PTEs, viz. arsenic, cadmium, cobalt, chromium, copper, iron, manganese, lead and zinc), which when present in high concentrations may pose health hazards and ecological risk. Contamination factor, degree of contamination, modified degree of contamination, metal pollution index, pollution load index, enrichment factor, geoaccumulation index and ecological risk index were also determined for these PTEs in the study area. Sediment and soil samples were found to be alkaline and non-saline (pH > 7.0; EC < 4500 µS cm-1) with sodium and potassium as major ions. Iron (mg kg-1) was found to be most abundant in sediments (1477.59-6512.45) and soils (922.64-12,455.00). Cadmium content in sediments exceeded the threshold value (0.99 mg kg-1) at 2 (pre-monsoon) and 3 (post-monsoon) sampling sites. In both seasons, cadmium (0.10-2.05) and cobalt (11.40-17.52) contents (mg kg-1) exceeded the threshold limits (0.06 and 8.00 respectively) in all roadside soils. Significant spatiotemporal variation (p ≤ 0.05) was observed for pH; EC; and calcium, magnesium, copper, iron and zinc contents. Low to moderate potential ecological risk was observed for both roadside soils (31.80-213.82) and sediments (41.47-236.73). Contamination factor, enrichment factor and geoaccumulation index for cadmium were highest in roadside soils (6.84, 46.91 and 2.19, respectively) and sediments (7.64, 167.46 and 2.35, respectively) due to settlement of coal fly ash released from the industrial setups, on sediments/soils of the study area.

Identification of binding residues between periplasmic adapter protein (PAP) and RND efflux pumps explains PAP-pump promiscuity and roles in antimicrobial resistance.

Active efflux due to tripartite RND efflux pumps is an important mechanism of clinically relevant antibiotic resistance in Gram-negative bacteria. These pumps are also essential for Gram-negative pathogens to cause infection and form biofilms. They consist of an inner membrane RND transporter; a periplasmic adaptor protein (PAP), and an outer membrane channel. The role of PAPs in assembly, and the identities of specific residues involved in PAP-RND binding, remain poorly understood. Using recent high-resolution structures, four 3D sites involved in PAP-RND binding within each PAP protomer were defined that correspond to nine discrete linear binding sequences or "binding boxes" within the PAP sequence. In the important human pathogen Salmonella enterica, these binding boxes are conserved within phylogenetically-related PAPs, such as AcrA and AcrE, while differing considerably between divergent PAPs such as MdsA and MdtA, despite overall conservation of the PAP structure. By analysing these binding sequences we created a predictive model of PAP-RND interaction, which suggested the determinants that may allow promiscuity between certain PAPs, but discrimination of others. We corroborated these predictions using direct phenotypic data, confirming that only AcrA and AcrE, but not MdtA or MsdA, can function with the major RND pump AcrB. Furthermore, we provide functional validation of the involvement of the binding boxes by disruptive site-directed mutagenesis. These results directly link sequence conservation within identified PAP binding sites with functional data providing mechanistic explanation for assembly of clinically relevant RND-pumps and explain how Salmonella and other pathogens maintain a degree of redundancy in efflux mediated resistance. Overall, our study provides a novel understanding of the molecular determinants driving the RND-PAP recognition by bridging the available structural information with experimental functional validation thus providing the scientific community with a predictive model of pump-contacts that could be exploited in the future for the development of targeted therapeutics and efflux pump inhibitors.

Appraisal of groundwater quality and associated risks in Mansa district (Punjab, India).

Mansa district in Malwa region of South-West Punjab has gained significant attention due to elevation in number of patients suffering from diverse diseases especially cancer and consumption of contaminated groundwater could be one of the possible reasons. The present study reports the assessment of 59 groundwater samples from Mansa district by evaluating physicochemical characteristics, potentially toxic element (PTE) contamination and associated health implications followed by analysis of water quality status using various indices. Multivariate statistics were applied for source identification of PTEs in groundwater. The study revealed occurrence of PTEs with mean (µg L-1) dominance order of As (650.8) > U (104.14) > Zn (55.3) > Fe (34.4) > Hg (8.3) > Mn (5.1) > Cu (4.1) > Cr (2.7) > Pb (2.4). One hundred and 71.19% groundwater samples were found to be seriously contaminated with As and U, respectively, and posing high cancer risks to local residents via ingestion. Higher hazard indices of 16.64 and 12.85 for children and adults, respectively, indicated high non-carcinogenic health risks to both population groups but children were observed to be more vulnerable. Correlation analysis showed positive correlations of U with total dissolved solids (TDS), fluoride (F-) and total alkalinity (TA). Principal component analysis (PCA) and cluster analysis (CA) revealed the contribution of both geogenic (weathering of rocks) and anthropogenic sources (overuse of agrochemicals in agricultural lands and release of inefficiently treated industrial effluents) for deteriorating the groundwater quality of study area. The study counsels the inhabitants to consume treated groundwater as ingestion route was identified as the primary route of exposure.

Quantitative assessment of exposure of heavy metals in groundwater and soil on human health in Reasi district, Jammu and Kashmir.

The assessment of heavy metal contents in environmental sectors is important to estimate the carcinogenic and non-carcinogenic doses and risks for the mankind associated with it. The present work deals with the assessment of the risk exposure related to heavy metal contents in groundwater and soil samples to two different age groups via three different transits, i.e., ingestion, inhalation and dermal. The concentrations of heavy metals (Zn, Cd, Cu, Pb and Cr) were measured in the villages of lower Himalayas of Reasi district by using microwave plasma atomic emission spectrometer. The calculated mean contamination factors of heavy metals in soil samples were as: Zn, 0.73; Cu, 0.70; Pb, 0.74; and Cr, 0.33; which led to pollution load index less than unity. The overall carcinogenic risks have been varied from 6.4E-08 to 5.1E-07 in soil samples and from 7.3E-06 to 1.1E-04 in ground water samples and were found to be well within the range prescribed by USEPA (Screening level ecological risk assessment protocol for hazardous waste combustion facilities, appendix E: toxicity reference values, US Environmental Protection Agency, Washington, D.C., 1999). The mean values of heavy metal contents except lead and chromium in water samples were found to be less than the values prescribed by various agencies. Geo-accumulation Index showed that Pb contribute to the highest contamination (0 < Igeo < 1) among the other heavy metals. Cluster analysis and principal component analysis identified that Zn, Cu, Pb and Cr had a relationship and the presence of these heavy metals could be related to vehicle emissions, traffic sources and industrial sources. The overall mean values of the non-carcinogenic doses and associated hazard risks in soil and water samples calculated for children were found to be higher than the adults which may be due to hand to mouth activities.

An AcOH-mediated metal free approach towards the synthesis of bis-carbolines and imidazopyridoindole derivatives and assessment of their photophysical properties.

An AcOH-mediated concise, atom-economical and environmentally sustainable tandem strategy has been formulated to access highly fluorescent (ΦF up to 40%) N-fused bis-carbolines, imidazopyrido[3,4-b]indoles and imidazo[1,5-a]pyridines via the formation of three C-N bonds in a single operation. The multicomponent character of the reaction, easy to execute reaction conditions, simple purification procedure and excellent light emitting properties of the product afforded thereof provide a huge scope.

Sorption technique as a tool for reduction of genotoxicity.

In the present study, the Allium cepa root chromosomal aberration assay was used to determine the genotoxic effects of copper and cadmium ions solutions before and after sorption processes. The sorption process was carried out using unmodified Dendrocalamus strictus charcoal powder, nitrilotriacetic acid (NTA)-modified D. strictus charcoal powder, and Saccharomyces cerevisiae. The frequency of total chromosomal aberrations was observed to be 24.30-45.13% for copper and 13.16-45.14% for cadmium at different concentrations (1-500 mg/l) before the sorption process. Both metal ions solutions resulted in significant reduction of chromosomal aberrations after all the modes of the sorption processes. However, the order of reduction of percentage chromosomal aberrations for copper and cadmium solutions was found to be 45.29-70.04% and 47.80-84.57%, respectively (NTA-modified D. strictus charcoal powder); >44.53-54.32% and 37.10-79.40%, respectively (unmodified D. strictus charcoal powder); >15.59-48.51% and 13.63-21.50%, respectively (S. cerevisiae).

Dendrocalamus strictus Charcoal: An Efficient Adsorbent for Removal of Cu (II) Ions from Aqueous Solution and its Applicability in the Reduction of Genotoxic Potential of Cu (II) Ions.

The present study pertains to evaluate the efficiency of Dendrocalamus strictus charcoal powder as an adsorbent to adsorb copper ions from aqueous solution under different conditions of pH, initial metal ion concentration, adsorbent dose, contact time, and temperature. Physical characterization of Dendrocalamus strictus charcoal powder was performed using different techniques such as scanning electron microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, Brunauer Emmett and Teller surface analysis and X-ray diffraction. Langmuir, Freundlich, and Temkin isotherm models were employed to describe the adsorption behavior of adsorbent in the removal of copper ions from aqueous solution. Thermodynamic parameters indicated that the adsorption of copper ions onto the surface of the adsorbent was feasible, spontaneous, and endothermic in nature. Data analysis using kinetic models revealed the pseudo-second-order as the suitable model to describe the process of adsorption. Studies were further carried out to analyze the genotoxic effects of copper ions in aqueous solution before and after adsorption, using Allium cepa assay. This study revealed that Dendrocalamus strictus charcoal powder could be applied as an alternative for more costly adsorbents in the detoxification of copper ions from aqueous solution.

Spectrophotometric determination of triclosan based on diazotization reaction: response surface optimization using Box-Behnken design.

A spectrophotometric method based on diazotization of aniline with triclosan has been developed for the determination of triclosan in water samples. The diazotization process involves two steps: (1) reaction of aniline with sodium nitrite in an acidic medium to form diazonium ion and (2) reaction of diazonium ion with triclosan to form a yellowish-orange azo compound in an alkaline medium. The resulting yellowish-orange product has a maximum absorption at 352 nm which allows the determination of triclosan in aqueous solution in the linear concentration range of 0.1-3.0 µM with R2 = 0.998. The concentration of hydrochloric acid, sodium nitrite, and aniline was optimized for diazotization reaction to achieve good spectrophotometric determination of triclosan. The optimization of experimental conditions for spectrophotometric determination of triclosan in terms of concentration of sodium nitrite, hydrogen chloride and aniline was also carried out by using Box-Behnken design of response surface methodology and results obtained were in agreement with the experimentally optimized values. The proposed method was then successfully applied for analyses of triclosan content in water samples.

Assessment of radon concentration and heavy metal contamination in groundwater of Udhampur district, Jammu & Kashmir, India.

Radon concentration was measured in water samples of 41 different locations from Udhampur district of Jammu & Kashmir, India, by using RAD7 and Smart RnDuo monitor. The variation of radon concentration in water ranged from 1.44 ± 0.31 to 63.64 ± 2.88 Bq L-1, with a mean value of 28.73 Bq L-1 using RAD7 and 0.64 ± 0.28 to 52.65 ± 2.50 Bq L-1, with a mean value of 20.30 Bq L-1 using Smart RnDuo monitor, respectively. About 17.07% of the studied water samples recorded to display elevated radon concentration above the reference range suggested by United Nation Scientific Committee on the Effects of Atomic Radiations (UNSCEAR). The mean annual effective dose of these samples was determined, and 78.95% samples were found to be within the safe limits set by World Health Organisation (WHO) and European Council (EU). The study revealed good agreement between the values obtained with two methods. Heavy metals (Zn, Cd, Fe, Cu, Ni, As, Hg, Co, Pb and Cr) were determined in water samples by microwave plasma atomic emission spectrometer, and their correlation with radon content was also analysed.

Estimation of arsenic, manganese and iron in mustard seeds, maize grains, groundwater and associated human health risks in Ropar wetland, Punjab, India, and its adjoining areas.

Present study was conducted to estimate the bioconcentration of total arsenic (t-As), manganese (Mn) and iron (Fe) in mustard seeds and maize grains cultivated in agricultural fields of Ropar wetland and its surroundings. Possible health risks posed to residents of study area via daily dietary intake of inorganic arsenic (i-As), manganese and iron via consumption of mustard seeds, maize grains and groundwater were also assessed. i-As content was determined form t-As using relevant conversion factor (i-As = t-As in groundwater and i-As = 70% t-As in food crops). Mustard seeds acted as accumulator of arsenic as mean bioconcentration factor (BCF) was > 1 for 66.67% of the samples. BCFs of t-As, Mn and Fe for mustard seeds and maize grains varied logarithmically with their respective concentrations in soil samples, except BCF for Mn in mustard seeds, which followed a linear model. Hazard quotient and hazard index values of i-As, Mn and Fe were found to be > 1 for mustard seeds and groundwater samples. Possible cancer risk was determined for i-As in mustard seeds, maize grains and groundwater samples > 1.00E-06. These results indicated that daily dietary intake of mustard seeds, maize grains and groundwater contaminated with i-As, Mn and Fe is highly unsafe as it may cause a high possibility of appearance of cancerous and non-cancerous health problems in human population of study area.

Activity-Dependent Palmitoylation Controls SynDIG1 Stability, Localization, and Function.

UNLABELLED: Synapses are specialized contacts between neurons. Synapse differentiation-induced gene I (SynDIG1) plays a critical role during synapse development to regulate AMPA receptor (AMPAR) and PSD-95 content at excitatory synapses. Palmitoylation regulates the localization and function of many synaptic proteins, including AMPARs and PSD-95. Here we show that SynDIG1 is palmitoylated, and investigate the effects of palmitoylation on SynDIG1 stability and localization. Structural modeling of SynDIG1 suggests that the membrane-associated region forms a three-helical bundle with two cysteine residues located at positions 191 and 192 in the juxta-transmembrane region exposed to the cytoplasm. Site-directed mutagenesis reveals that C191 and C192 are palmitoylated in heterologous cells and positively regulates dendritic targeting in neurons. Like PSD-95, activity blockade in a rat hippocampal slice culture increases SynDIG1 palmitoylation, which is consistent with our prior demonstration that SynDIG1 localization at synapses increases upon activity blockade. These data demonstrate that palmitoylation of SynDIG1 is regulated by neuronal activity, and plays a critical role in regulating its stability and subcellular localization, and thereby its function. SIGNIFICANCE STATEMENT: Palmitoylation is a reversible post-translation modification that has recently been recognized as playing a critical role in the localization and function of many synaptic proteins. Here we show that activity-dependent palmitoylation of the atypical AMPA receptor auxiliary transmembrane protein SynDIG1 regulates its stability and localization at synapses to regulate function and synaptic strength.

Quantitative assessment of possible human health risk associated with consumption of arsenic contaminated groundwater and wheat grains from Ropar Wetand and its environs.

Arsenic (As) is a carcinogenic metalloid that enters food chain through food and water and poses health risk to living beings. It is important to assess the As status in the environment and risks associated with it. Hence, a risk assessment study was conducted across Ropar wetland, Punjab, India and its environs in pre-monsoon season of 2013, to estimate the risk posed to adults and children via daily consumption of As contaminated groundwater and wheat grains. Arsenic concentrations determined in groundwater, soil and wheat grain samples using atomic absorption spectrometer ranged from 2.90 to 10.56 µg L(-1), 0.06 to 0.12 mg kg(-1) and 0.03 to 0.21 mg kg(-1), respectively. Arsenic in wheat grains showed significant negative correlation with phosphate content in soil indicating a competitive uptake of arsenate and phosphate ions by plants. Principal component analysis and cluster analysis suggested that both natural and anthropogenic factors contribute to variation in As content and other variables studied in soil and groundwater samples. Total cancer risk and hazard index were higher than the USEPA safety limits of 1.00 × 10(-6) and 1, respectively, for both adults and children indicating a high risk of cancer and other health disorders. Consumption of As contaminated wheat grains was found to pose higher risk of cancer and non-cancer health disorders as compared to intake of As contaminated groundwater by both adults and children. Moreover, children were found to be more prone to cancer and other heath disorders due to As exposure via wheat grains and groundwater as compared to adults.

Removal of cadmium ion from wastewater by carbon-based nanosorbents: a review.

A green environment and a healthy life are dream projects of today's science and technology to save the world. Heavy metal ions in water affect both environment and human health. Cadmium has been identified as one of the heavy metals that causes acute or chronic toxic effects if ingested. Increasing use of cadmium in different technological fields has raised concern about its presence and removal from water/wastewater. Researchers have made many systematic efforts to remove heavy metals from water to reduce their impact on human beings and the environment. Adsorption is one of the best methods to remove heavy metals from water among the different proposed methods. This study explores carbon-based nanosorbents which have been proved as effective adsorbents for removal of cadmium ions from water. The adsorption efficiency of carbon-based nanosorbents is the main criterion to rank and select them for removal of cadmium ions from water. Toxicity, reusability and environmentally friendly characteristics of sorbents are also taken considered while ranking the suitable carbon-based nanosorbents for removal of cadmium ions from water.

Self-assembled monolayer of 2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) on gold surface: A platform for impedimetric and potentiometric sensing of mercury(II).

2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) was synthesized, self-assembled on the surface of gold (Au) electrode (Au-MTP) followed by characterization using Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). CV and EIS confirmed the formation of well-organized Au-MTP SAM free from defects and pinholes. Au-MTP was further utilized as a platform for sensing of Hg2+ using EIS. The results showed sensitive and selective response of Au-MTP towards Hg2+ in the linear concentration range from 1.0 × 10-10 M to 1.0 × 10-4 M with limit of detection (LoD) of 5.6 × 10-11 M. Furthermore, MTP was self-assembled on gold nanoparticles (AuNPs) and MTP bound gold nanoparticles (MTP-AuNPs) so obtained were used as modifier for construction of carbon paste electrode (CPE). Hg2+-CPE exhibited Nernstian response towards Hg2+ with slope of 28.3 mV/decade in the concentration range from 1.0 × 10-5 M to 1.0 × 10-1 M with LoD of 6.3 × 10-6 M. Both the Au-MTP EIS sensor and Hg2+-CPE were successfully applied for estimation of Hg2+ content in tap water samples.

S-S bridged Schiff bases as versatile ionophores: Synthesis and application for electrochemical sensing of Copper(II) and Mercury(II).

Schiff base derivates (3, 4 and 5) comprising pseudo cavity with different heteroatoms (O, N and S) were designed, synthesized and explored for their detection behaviour towards diverse metal ions. In UV and fluorescence studies, all three receptors exhibited sensitive response towards Cu2+ while 5 showed sensitivity for Hg2+ also. To explore the synthesized receptors for electrochemical behaviour, voltammetric studies were conducted where 3, 4 and 5 exhibited sensitive response towards Cu2+ with detection limits of 9.8 × 10-7 M, 9.0 × 10-7 M and 1.41 × 10-7 M, respectively. The receptor 5 also showed response towards Hg2+ with detection limit of 5.61 × 10-8 M. The formation of complexes, 3/4+Cu2+ and 5+Cu2+/Hg2+ was supported by large values of binding constant and associated negative free energy change. The binding mechanism of 3, 4 and 5 towards respective metal ions was confirmed using 1H-NMR and HR-MS studies. Further, to utilize the proposed sensors for on-site monitoring of analyte metal ions, carbon paste electrodes (CPEs) were constructed by incorporating 3, 4 and 5. All CPEs showed Nernstian response with lower detection limits and excellent selectivity and successfully utilized for the determination of Cu2+ and Hg2+ in groundwater samples.

Reversal of Peripheral Anterior Synechiae After Trabeculectomy With Argon Laser Synechiolysis.

We report a case of successful argon laser synechiolysis as a non-invasive alternative for peripheral anterior synechiae release after trabeculectomy in a young patient with steroid-induced ocular hypertension. Steroid-induced ocular hypertension is a known complication of vernal keratoconjunctivitis due to prolonged treatment with steroids. In refractive conditions, augmented trabeculectomy becomes the surgery of choice in these patients. In this article, we report successful treatment of iris tissue plugging the internal ostium with an argon laser and reinstatement of aqueous flow.

Modification of electrode surfaces by self-assembled monolayers of thiol-terminated oligo(phenyleneethynylene)s.

The wire-like properties of four S-(4-{2-[4-(2-phenylethynyl)phenyl]ethynyl}phenyl) thioacetate derivatives, PhC≡CC(6)H(4)C≡CC(6)H(4)SAc (1), H(2)NC(6)H(4)C≡CC(6)H(4)C≡CC(6)H(4)SAc (2), PhC≡CC(6)H(2)(OMe)(2)C≡CC(6)H(4)SAc (3) and AcSC(6)H(4)C≡CC(6)H(4)C≡CC(6)H(4)SAc (4) (Figure 1), all of which possess a high degree of conjugation along the oligo(phenyleneethynylene) (OPE) backbone, were investigated as self-assembled monolayers (SAMs) on gold and platinum electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The redox probe [Fe(CN)(6)](4)(-) was used in both the CV and impedance experiments. The results indicate that the thiolates derived from thioacetate-protected precursor molecules 1 and 2 form well-ordered monolayers on a gold electrode, whereas SAMs derived from 3 and 4 exhibit randomly distributed pinholes. The electron tunnelling resistance and fractional coverage of SAMs of all four compounds were examined using electron tunnelling theory. The analysis of the results reveal that the well-ordered SAMs of 1 and 2 exhibit higher charge-transfer resistance in comparison to the defect-ridden SAMs of 3 and 4. The additional steric bulk offered by the methoxy groups in 3 is likely to prevent efficient packing within the SAM, leading to a microelectrode behaviour, when assembled on a gold electrode surface. The protected dithiol derivative 4 probably binds to the surface through both terminal groups which prevents dense packing and leads to the formation of a monolayer with randomly distributed pinholes. Atomic force microscopy (AFM) was used to examine the morphology of the monolayers, and height images gave root-mean-square (RMS) roughness's which are in agreement with the proposed SAM structures.