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Unnatural amino acids have gained significant attention in protein engineering and drug discovery as they allow the evolution of proteins with enhanced stability and activity. The incorporation of unnatural amino acids into proteins offers a rational approach to engineer enzymes for designing efficient biocatalysts that exhibit versatile physicochemical properties and biological functions. This review highlights the biological and synthetic routes of unnatural amino acids to yield a modified protein with altered functionality and their incorporation methods. Unnatural amino acids offer a wide array of applications such as antibody-drug conjugates, probes for change in protein conformation and structure–activity relationships, peptide-based imaging, antimicrobial activities, etc. Besides their emerging applications in fundamental and applied science, systemic research is necessary to explore unnatural amino acids with novel side chains that can address the limitations of natural amino acids.

Synthesis, characterization, and ultrafast dynamics of porphyrin- and zinc porphyrin-based nanomaterials are reported. Spherical nanoparticles composed of a group of uniform materials based on orga...

Antibiotics, nowadays, are not only used for the treatment of human diseases but also used in animal and poultry farming to increase production. Overuse of antibiotics leads to their circulation in the food chain due to unmanaged discharge. These circulating antibiotics and their residues are a major cause of antimicrobial resistance (AMR), so comprehensive and multifaceted measures aligning with the One Health approach are crucial to curb the emergence and dissemination of antibiotic resistance through the food chain. Different chromatographic techniques and capillary electrophoresis (CE) are being widely used for the separation and detection of antibiotics and their residues from food samples. However, the matrix present in food samples interferes with the proper detection of the antibiotics, which are present in trace concentrations. This review is focused on the scientific literature published in the last decade devoted to the detection of antibiotics in food products. Various extraction methods are employed for the enrichment of antibiotics from a wide variety of food samples; however, solid-phase extraction (SPE) techniques are often used for the extraction of antibiotics from food products and biological samples. In addition, this review has scrutinized how changing instrumental composition, organization, and working parameters in the chromatography and CE can greatly impact the identification and quantification of antibiotic residues. This review also summarized recent advancements in other detection methods such as immunological assays, surface-enhanced Raman spectroscopy (SERS)-based assays, and biosensors which have emerged as rapid, sensitive, and selective tools for accurate detection and quantification of traces of antibiotics.

Actinomycetes are natural architects of numerous secondary metabolites including antibiotics. With increased multidrug-resistant (MDR) pathogens, antibiotics that can combat such pathogens are urgently required to improve the health care system globally. The characterization of actinomycetes available in Nepal is still very much untouched which is the reason why this paper showcases the characterization of actinomycetes from Nepal based on their morphology, 16S rRNA gene sequencing, and metabolic profiling. Additionally, antimicrobial assays and liquid chromatography-high resolution mass spectrometry (LC-HRMS) of ethyl acetate extracts were performed. In this study, we employed a computational-based dereplication strategy for annotating molecules which is also time-efficient. Molecular annotation was performed through the GNPS server, the SIRIUS platform, and the available databases to predict the secondary metabolites. The sequencing of the 16S rRNA gene revealed that the isolates BN6 and BN14 are closely related to Streptomyces species. BN14 showed broad-spectrum antibacterial activity with the zone of inhibition up to 30 mm against Staphylococcus aureus (MIC: 0.3051 µg/mL and MBC: 9.7656 µg/mL) and Shigella sonnei (MIC: 0.3051 µg/mL and MBC: 4.882 µg/mL). Likewise, BN14 also displayed significant inhibition to Acinetobacter baumannii, Klebsiella pneumoniae, and Salmonella typhi. GNPS approach suggested that the extracts of BN6 and BN14 consisted of diketopiperazines ((cyclo(D-Trp-L-Pro), cyclo(L-Leu-L-4-hydroxy-Pro), cyclo(L-Phe-D-Pro), cyclo(L-Trp-L-Pro), cyclo(L-Val-L-Pro)), and polypeptide antibiotics (actinomycin D and X2). Additional chemical scaffolds such as bacterial alkaloids (bohemamine, venezueline B, and G), anthramycin-type antibiotics (abbeymycin), lipase inhibitor (ebelactone B), cytocidal (oxopropaline D), antifungal and antitumor antibiotics (reductiomycin, streptimidone, deoxynybomycin), alaremycin, fumaramidmycin, anisomycin, and others were also annotated, which were further confirmed by using the SIRIUS platform, and literature survey. Thus, the bioprospecting of natural products from Streptomyces species from Nepal could be a potential source for the discovery of clinically significant and new antimicrobial agents in the future.

Gas chromatography columns fabricated using microelectromechanical system (MEMS) technology provide a number of clear advantages. However, successful deposition of stationary phases having a wide application range remains an important technical challenge. In this paper, we report, for the first time, on the deposition of room temperature ionic liquids (RTILs)—a versatile class of stationary phases—inside the channels of semi-packed columns (SPCs) for high-performance gas chromatographic separation of complex chemical mixtures. A 1 m long, 240 μm deep, 190 μm wide column comprising an array circular micropillars of 20 μm in diameter and 40 μm post spacing was fabricated using MEMS processes. Two RTILs were immobilized inside these columns using a dynamic coating method, and the columns were tested for separation of three different mixtures: a 15-component mixture of hazardous chemical pollutants, an 8-component mixture of fatty acid methyl esters, and a sample of gasoline. These columns displayed sharp and symmetrical peaks, significant selectivity variation between the two columns, and rapid separation times. The columns yielded high separation efficiencies measured by approximately 2300 plates/m under isothermal conditions. This work highlights the potential of RTILs to be used as excellent stationary phases for SPCs, thereby dramatically expanding the range of complex mixtures that could be analyzed using a micro gas chromatograph.

Gas chromatography is a technology that is constantly moving forward. The current trend for this field is moving towards miniaturizing the columns towards achieving high-speed separations. Groups are constantly researching different geometries, topographies, and stationary phases in order to make these separations more efficient. In order to achieve this goal of increased efficiency, we have taken two ideas from previous works, namely being width modulated channels as well as semi-packed columns, and tried to use the redeeming qualities that exist in both and combine them to achieve something that shares their positive points. Semi-packed columns have been shown to increase the plate height for a column. However, the pressure drop that occurs in these types is a significant drawback that makes high-speed separations very difficult to achieve with lower inlet pressures. Width modulation of the column channel can be used to change the overall velocity of the gas as it travels throughout the column resulting in a lower overall pressure drop. The method that was used to combine these two ideas was to change the density of the pillars in the semi-packed column along the length of the channel to achieve the same effect of the width modulation. This was achieved by changing the number of pillars across in the channel as well as the pitch distance between sets of pillars. Controls were also fabricated so the results could be compared to the two extreme designs. After extensive testing, the results indicated that between the minimum and maximum density, the maximum density allowed only ~50% of the total flow that the minimum density design showed at the same inlet pressure. In comparison, the design that changed pillar density throughout the channel allowed ~89% of the flow the minimum density design. This is a significant increase in flow and allows for much more to pass through the chip in a given time span increasing the efficiency of high-speed separations. The other factor that was tested for was the number of theoretical plates for each of the designs. It was shown through testing with a constant sample that the minimum density column behaves very similarly to an open column without pillars whereas the density modulated column has plate numbers between those of the minimum density and the maximum density. This is even further data that supports the use of a pillar density modulated chip for high-speed separations.

Porphyrin-based GUMBOS and nanoGUMBOS were synthesized for potential application as improved photosensitizing materials. In this study, porphyrin dyes [meso-tetra(4-carboxyphenyl)porphine (TCPP) and zinc(II) meso-tetra(4-carboxyphenyl)porphine (Zn-TCPP)] were selected as anions, and trihexyltetradecylphosphonium (P66614) was employed as a cation. The resulting [P66614]4[TCPP] and [P66614]4[Zn-TCPP] GUMBOS (group of uniform materials based on organic salts) provided high photostability and excellent thermal stability for these compounds. NanoGUMBOS, i.e., nanomaterials derived from GUMBOS, were synthesized using reprecipitation and ion association methods. The surface charges of these nanoparticles were tuned from positive to negative through use of an ion association synthetic method without the need for additives or stabilizers. When compared to the parent dyes, nanoGUMBOS exhibited excellent photodynamic properties for potential applications as photosensitizers. Evaluation of the electrochemical propert...

Among a number of gas analyzers, portable gas chromatography (GC) systems created by the integration of microfabricated components are promising candidates for rapid and on-site analysis of a number of complex chemical mixtures. This Feature provides a snapshot of the progress made in developing micro gas chromatography (μGC) systems in the last 4 decades. In particular, we discuss the development of microfabricated preconcentrators, separation columns, and detectors. Furthermore, we review different stationary phase materials used to coat the separation columns and the major efforts toward the development of an integrated μGC.

These studies demonstrate the influence of an intermediate layer of aluminum oxide on the separation performance of a room temperature ionic liquid (RTIL)-coated gas chromatography silicon microcolumn. A 1 m long semipacked column having 190 μm wide and 240 μm deep rectangular cross-sectional channels with embedded arrays of micro pillars was microfabricated. A thin layer of alumina was then deposited on the surface of the channels via atomic layer deposition. Following the alumina deposition, the channels were coated with an RTIL. The separation performance of the RTIL-coated columns with and without the alumina layer was evaluated by measuring the separation efficiency and peak capacity. A substantial increase in separation efficiency was observed in the presence of the alumina layer. The alumina-pretreated columns, at optimum flow rate, exhibited as high as 8000 plates per meter, which is a 2.1-fold increase as compared to the column with no alumina layer. It is inferred that alumina coating promotes the formation of a more uniform RTIL film, thereby enhancing the separation efficiency. The peak production rates of alumina-RTIL columns for temperature-programmed separation were found to be 0.80–1.1 peaks per second, which is an improvement compared to silicon-RTIL columns. The separation performance of these columns were further evaluated by separating a standard 21-component mixture of hazardous organic compounds, a sample of kerosene, diesel, and B20 biodiesel. These studies open up new possibilities of enhancing the separation efficiency of microcolumns by coating silicon surface with a suitable material prior to depositing an ionic liquid.

In this study, GUMBOS (a group of uniform materials based on organic salts) derived from rhodamine B chloride, 1,1′-diethyl-2,2′-carbocyanine iodide, 3,3′-diethylthiacarbocyanine iodide, and meso-tetra(4-carboxyphenyl)porphine were synthesized and characterized for application as energy relay dyes (ERDs) in dye-sensitized solar cells (DSSCs). A facile ion exchange reaction was employed for synthesis of GUMBOS. These GUMBOS exhibited improved characteristics in comparison to their respective parent dyes, including increased solubility, thermal stability, molar extinction coefficient, and fluorescence quantum yield. In addition, excellent spectral overlap integral and Forster resonance energy transfer efficiency were observed between various GUMBOS based-ERDs (donors) and the photosensitizing dye, N719 [di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II)] (acceptor). DSSC devices were fabricated and solar efficiency was evaluated in the absence and presence of ERDs using N719 as the photosensitizing dye. DSSCs in the presence of GUMBOS-based ERDs exhibited increased solar efficiencies in comparison to DSSCs in the absence of ERDs. Moreover, increases in solar efficiencies were found to be dependent on the counterions used in GUMBOS synthesis.

Herein, we demonstrate an alternative strategy for creating QCM-based sensor arrays by use of a single sensor to provide multiple responses per analyte. The sensor, which simulates a virtual sensor array (VSA), was developed by depositing a thin film of ionic liquid, either 1-octyl-3-methylimidazolium bromide ([OMIm][Br]) or 1-octyl-3-methylimidazolium thiocyanate ([OMIm][SCN]), onto the surface of a QCM-D transducer. The sensor was exposed to 18 different organic vapors (alcohols, hydrocarbons, chlorohydrocarbons, nitriles) belonging to the same or different homologous series. The resulting frequency shifts (Δf) were measured at multiple harmonics and evaluated using principal component analysis (PCA) and discriminant analysis (DA) which revealed that analytes can be classified with extremely high accuracy. In almost all cases, the accuracy for identification of a member of the same class, that is, intraclass discrimination, was 100% as determined by use of quadratic discriminant analysis (QDA). Impressively, some VSAs allowed classification of all 18 analytes tested with nearly 100% accuracy. Such results underscore the importance of utilizing lesser exploited properties that influence signal transduction. Overall, these results demonstrate excellent potential of the virtual sensor array strategy for detection and discrimination of vapor phase analytes utilizing the QCM. To the best of our knowledge, this is the first report on QCM VSAs, as well as an experimental sensor array, that is based primarily on viscoelasticity, film thickness, and harmonics.

Metal complexes of porphyrins and phthalocyanines are attractive materials for designing recognition elements for chemical sensors, and hence they have been the focus of intense research. An interesting feature of these materials is that they can be functionalized at multiple positions to create sensors having slightly different selectivities. Considering the importance of these materials, herein, we report the synthesis and vapor-sensing characteristics of novel porphyrin- and phthalocyanine-based GUMBOS. More specifically, sodium counterions of copper (II) meso-tetra (4-carboxyphenyl) porphyrin (CuTCPP) and copper phthalocyanine-3,4ʹ,4″,4‴-tetrasulfonic acid (CuPcS4) were replaced by trihexyl(tetradecyl)phosphonium cations to respectively produce the GUMBOS compounds, [P66614]4[CuTCPP] and [P66614]4[CuPcS4]. The resulting compounds were found to be solids with considerably lower melting points. These GUMBOS were then coated on the surface of a quartz crystal resonator, and the vapor sensing characteristics were evaluated by exposing the sensors to 11 different organic vapors. These materials exhibited excellent sensing characteristics; moreover, the two sensors exhibited cross-reactive response patterns, making these compounds very promising candidates for array-based vapor-sensing applications.

For gas chromatography, the separation column is the most important component in influencing performance of a gas chromatography system. The semi-packed MEMS column design has been widely used because it enhances the separation efficiency and provides higher sample capacity. However, a limitation of this type of column is the large pressure drop that occurs across its column length. This paper reports a new semi-packed design that utilizes density modulation of the micro-pillars to improve the pressure drop and increase the separation efficiency for high speed separations.

RATIONALE Detection of hydrophobic peptides remains a major obstacle for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). This stems from the fact that most matrices for MALDI are hydrophilic and therefore have low affinities for hydrophobic peptides. Herein, 1-aminopyrene (AP) and AP-derived group of uniform materials based on organic salts (GUMBOS) as novel matrices for MALDI-MS analyses of peptides were investigated for hydrophobic and hydrophilic peptides. METHODS A number of solid-phase AP-based GUMBOS are synthesized with variable hydrophobicity simply by changing the counterions. Structures were confirmed by use of 1H NMR and electrospray ionization mass spectrometry (ESI-MS). 1-Octanol/water partition coefficients (Ko/w) were used to measure the hydrophobicity of the matrices. A dried-droplet method was used for sample preparation. All spectra were obtained using a MALDI-TOF mass spectrometer in positive ion reflectron mode. RESULTS A series of AP-based GUMBOS was synthesized including [AP][chloride] ([AP][Cl]), [AP][ascorbate] ([AP][Asc]) and [AP][bis(trifluoromethane)sulfonimide] ([AP][NTf2]). The relative hydrophobicities of these compounds and α-cyano-4-hydroxycinnamic acid (CHCA, a common MALDI matrix) indicated that AP-based GUMBOS can be tuned to be much more hydrophobic than CHCA. A clear trend is observed between the signal intensities of hydrophobic peptides and hydrophobicity of the matrix. CONCLUSIONS MALDI matrices of GUMBOS with tunable hydrophobicities are easily obtained simply by varying the counterion. We have found that hydrophobic matrix materials are very effective for MALDI determination of hydrophobic peptides and, similarly, the more hydrophilic peptides displayed greater intensity in the more hydrophilic matrix. Copyright © 2014 John Wiley & Sons, Ltd.

We describe a method for dispersive liquid-liquid microextraction of nitrotoluene-based compounds. This method is based on use of the room temperature ionic liquid (RTIL) 1-hexyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide as the accepting phase, and is shown to work well for extraction of 4-nitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene. Separation and subsequent detection of analytes were accomplished via HPLC with UV detection. Several parameters that influence the efficiency of the extraction were optimized using experimental design. In this regard, a Plackett–Burman design was used for initial screening, followed by a central composite design to further optimize the influencing variables. For a 5-mL water sample, the optimized IL-DLLME procedure requires 26 mg of the RTIL as extraction solvent and 680 μL of methanol as the dispersant. Under optimum conditions, limits of detection (LODs) are lower than 1.05 μg L−1. Relative standard deviations for 6 replicate determinations at a 4 μg L−1 analyte level are 0.998 were achieved. This method was successfully applied to extraction and determination of nitrotoluene-based compounds in spiked tap and lake water samples.

Summary Daphnia are key species in lake ecosystems and are a model system in ecology. Their ecological success is very much due to their dual reproductive mode: females reproduce parthenogenetically when environmental conditions are favourable but switch to sexual reproduction and resting egg production in unfavourable conditions such as winter. Phases of clonal reproduction lower the overall genotypic diversity of Daphnia populations due to the random loss of genotypes. During phases of sexual reproduction, new genotypes enhance the genotypic variability of the population and compensate for the loss of clonal lineages. We hypothesised that clonal diversity should be low during the winter months due to high mortality rates (clonal erosion) but will be restored in the spring most likely from the resting egg bank. To test this hypothesis, we investigated the clonal composition of a Daphnia pulex population in a small mesotrophic lake in Norway. Daphnia were sampled every month from September 2007 to September 2010, and c. 60 individuals per month were genotyped using 11 microsatellite markers. Marker resolution was high, and 582 different genotypes could be detected in the 936 individuals analysed. An unexpected complication for the study was the illegal introduction of planktivorous fish into the lake between autumn 2006 and spring 2007. This led to significant predation pressure on the D. pulex population and shifted the cladoceran community to smaller species. However, while the D. pulex population density declined severely over the study years, the overall genotypic variability increased. We observed very high turnover rates, with many clones being present for only a single month. Nevertheless, and as expected, genotypic diversity was higher during summer and lower during winter, and some parthenogenetic individuals seemed to be able to survive the winter. The large majority of new genotypes came from the resting egg bank. We conclude that, due to the new predation pressure, the resting egg bank has become much more important in restocking genotypic diversity as well as for D. pulex abundance. However, despite the buffering capacities of the resting egg bank, the predation pressure will most likely lead to the extinction of D. pulex in Lake Myravatn.

Herein, we report a fluorescein-based room temperature ionic liquid (RTIL) as a fluorescent probe for highly selective and sensitive detection of albumins. This RTIL was prepared by pairing dianionic fluorescein (FL) with trihexyl(tetradecyl)phosphonium (P66614) cation. The ionic liquid was then dispersed in aqueous medium to produce nanodroplet dispersions. Examination of fluorescence and UV-vis spectroscopic data suggests that these dispersions are comprised of strongly fluorescent monomeric species and weakly fluorescent J-type aggregates. The relative abundance of these two types of species is observed to be dependent on the type and concentration of proteins. In the presence of bovine serum albumin (BSA) or human serum albumin (HSA), monomeric species are found to be predominant, and hence an increase in fluorescence intensity was observed with increasing concentrations of BSA or HSA. Excellent correlation between fluorescence intensity and HSA concentration was observed, and concentrations as low as 300 ng per mL of HSA were detectable. Overall, these [P66614]2[FL] nanodroplets appear to be very promising materials for facile, inexpensive, rapid, and label-free detection of albumins in aqueous medium with a high degree of accuracy, sensitivity, and selectivity.

Development of ionic liquid (IL)-based colorimetric sensor arrays for detection and identification of chemicals in both the aqueous and vapor phases is reported. These facile and inexpensive optoelectronic sensors were fabricated by using ionic liquids (ILs) derived from readily available pH indicator dyes. A series of 12 different chemosensory ILs were synthesized by pairing anionic pH indicator dyes with trihexyl(tetradecyl)phosphonium ([P66614]) cation via an ion exchange reaction. The incorporation of the [P66614] cation imparted hydrophobic characteristics to these ILs, and this induced hydrophobicity led to their desired low solubility in aqueous solutions, as well as eliminated the need for a specialized hydrophobic matrix/substrate for immobilization. In this manuscript, four different matrices, i.e. glass microfiber filter papers, cotton threads, silica thin layer chromatography (TLC) plates, and alumina TLC plates, were employed for fabrication of sensor arrays. These sensor arrays were used to analyze pH values of aqueous solutions as well as for detection of acidic and basic vapors. To further prove the applicability of these IL sensor arrays as tools to sense closely related complex materials, the arrays were applied to successful discrimination of aqueous solutions of smoke from three commercially available cigarettes. The digital data generated from these sensor arrays were used in developing predictive models for accurately identifying various analytes. Two approaches were used for developing the models, and two methods were applied for assessing the predictive accuracy of the models. Use of cotton threads as a matrix led to development of a more flexible, low volume, and lightweight array to estimate pH and detect a variety of vapors. These wearable arrays may possibly be incorporated into bandages, sweatbands, diapers, and similar systems. Overall, these IL-based sensor arrays should provide a new research direction in the development of advanced colorimetric sensor arrays for detection and identification of a range of analytes relevant to many different applications.

Ionic liquids (ILs) are rapidly emerging as important coating materials for highly sensitive chemical sensing devices. In this regard, we have previously demonstrated that a quartz crystal microbalance (QCM) coated with a binary mixture of an IL and cellulose acetate can be employed for detection and molecular weight estimation of organic vapors (J. Mater. Chem. 2012, 22, 13732). Herein, we report follow-up studies aimed at formulating the theoretical basis for our previously observed relationship between molecular weight and changes in the QCM parameters. In the current work, we have investigated the vapor sensing characteristics of a series of binary blends of ILs and polymers over a wider concentration range of analytes, and a quadratic equation for estimating the approximate molecular weight of an organic vapor is proposed. Additionally, the frequency (f) and dissipation factor (D) at multiple harmonics were measured by use of a quartz crystal microbalance with dissipation monitoring (QCM-D). These QCM-D data were then analyzed by fitting to various models. It is observed that the behavior of these films can be best described by use of the Maxwell viscoelastic model. In light of these observations, a plausible explanation for the correlation between the molecular weight of absorbed vapors and the QCM parameters is presented. Our previous findings appear to be a special case of this more general observation. Overall, these results underscore the true potential of IL-based composite materials for discrimination and molecular weight estimation of a broad range of chemical vapors.

Summary Eurasian perch (Perca fluviatilis), a non-native planktivorous fish species in western Norway, has been released into Lake Myravatn, which previously lacked planktivorous fish. Prior to the introduction, the zooplankton community was structured by predation by larvae of the phantom midge (Chaoborus flavicans), which maintained a bivoltine life cycle in the lake. We hypothesised that the perch introduction would diminish the density and alter the bivoltine life-cycle pattern of Chaoborus. To assess this, we used time series data from before (1983) and after (2007–10) the perch introduction. The perch appears to have effectively exterminated the previously dominant predator C. flavicans within 4–5 years of introduction into the lake. The density of the larvae in the water column was high in 1983 as well as in 2007, with maximum levels recorded in August (up to 15 400 individuals m−2). In 2008, larval density was lower than in previous years, but the most dramatic decline occurred in 2009 (maximum 212 individuals m−2). In 2010, the density was very low (maximum 11 individuals m−2), and after July 2010, no larvae were found in the water column. The number of larvae residing in the sediments also declined quickly after the perch introduction. In 1983 and 2007, C. flavicans produced two generations per year. Following the first emergence and reproduction in May, young larvae appeared in June and developed rapidly to emergence and reproduced again in August. Young larvae appeared again in August–September. In 2008, young larvae appeared only in June with no second emergence and reproduction. In 2009, young larvae did not appear until July, and again no further reproduction took place. Only a few instar IV larvae were recorded in 2010. The collapse in life cycle into a univoltine pattern occurred prior to the main population decline. We conclude that direct predation by perch on Chaoborus larvae is the most likely explanation for the observed changes in their life cycle and density. It appears that the C. flavicans population of Lake Myravatn is approaching extinction.

A novel approach for tuning spectral properties, as well as minimizing aggregation, in zinc porphyrin and zinc phthalocyanine-based compounds is presented. Particular emphasis is placed on use of these compounds as photosensitizers in photodynamic therapy (PDT). To accomplish this aim, a bulky hydrophobic cation, trihexyltetradecylphosphonium, is paired with anionic porphyrin and phthalocyanine dyes to produce a group of uniform materials based on organic salts (GUMBOS) that absorb at longer wavelengths with high molar absorptivity and high photostability. Nanoparticles derived from these GUMBOS possess positively charged surfaces with high zeta potential values, which are highly desirable for PDT. Upon irradiation at longer wavelengths, these GUMBOS produced singlet oxygen with greater efficiency as compared to the respective parent dyes.

Detection of hydrophobic peptides remains a major obstacle for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). This stems from the fact that most matrices for MALDI are hydrophilic and therefore have low affinities for hydrophobic peptides. Herein, 1-aminopyrene (AP) and AP-derived group of uniform materials based on organic salts (GUMBOS) as novel matrices for MALDI-MS analyses of peptides were investigated for hydrophobic and hydrophilic peptides.A number of solid-phase AP-based GUMBOS are synthesized with variable hydrophobicity simply by changing the counterions. Structures were confirmed by use of (1)H NMR and electrospray ionization mass spectrometry (ESI-MS). 1-Octanol/water partition coefficients (Ko/w) were used to measure the hydrophobicity of the matrices. A dried-droplet method was used for sample preparation. All spectra were obtained using a MALDI-TOF mass spectrometer in positive ion reflectron mode.A series of AP-based GUMBOS was synthesized including [AP][chloride] ([AP][Cl]), [AP][ascorbate] ([AP][Asc]) and [AP][bis(trifluoromethane)sulfonimide] ([AP][NTf2]). The relative hydrophobicities of these compounds and α-cyano-4-hydroxycinnamic acid (CHCA, a common MALDI matrix) indicated that AP-based GUMBOS can be tuned to be much more hydrophobic than CHCA. A clear trend is observed between the signal intensities of hydrophobic peptides and hydrophobicity of the matrix.MALDI matrices of GUMBOS with tunable hydrophobicities are easily obtained simply by varying the counterion. We have found that hydrophobic matrix materials are very effective for MALDI determination of hydrophobic peptides and, similarly, the more hydrophilic peptides displayed greater intensity in the more hydrophilic matrix.

A novel vapor-sensitive composite film comprising cellulose acetate and a representative compound (1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate) from a Group of Uniform Materials Based on Organic Salts (GUMBOS) has been developed and characterized. The vapor sensing characteristics of the film is investigated using a quartz crystal microbalance (QCM) transducer. The material exhibited greatly improved performance characteristics toward a number of organic vapors. It is demonstrated that the ratio of the change in resonance frequency (Δf) to the change in motional resistance (ΔR) is a concentration-independent quantity proportional to the molecular weight of the absorbed chemical species. To the best of our knowledge, this is the first study to show a direct relationship between Δf/ΔR and the molecular weight of analytes. This unique finding should prove extremely useful for easy identification and molecular weight determination of a broad range of chemical vapors.