Low Molecular Mass Compounds Research Articles

Development of a Microwave-Assisted Bench Reactor for Biomass Pyrolysis Using Hybrid Heating.

Microwave-assisted pyrolysis (MAP) is a cutting-edge technology that converts biomass into fuels, chemicals, and materials. In this study, an Arduino was used to control and automate a MAP system built from a microwave oven with a cordierite chamber filled with silicon carbide. Sugar cane bagasse was pyrolyzed at 250, 350, 450, and 550 °C to validate the MAP system and obtain pyrolytic products with different yields and chemical compositions. Lower temperatures led to high biochar yields, but the highest surface area of 25.14 m2 g-1 was only achieved at 550 °C. By contrast, higher temperatures favored the recovery of pyrolysis liquids. BET and scanning electron microscopy analyses revealed a porous biochar structure, while Fourier transform infrared spectroscopy analysis showed that the availability of functional groups on the biochar surface decreased with an increase in pyrolysis temperature. GC-MS analysis quantified valuable low molecular mass compounds in pyrolysis liquids, including aldehydes, ketones, phenols, and alcohols. With its unprecedented hybrid heating device, the MAP system promoted suitable heating rates (31.9 °C min-1) and precise temperature control (only 19 °C of set point variation), generating pyrolysis products devoid of microwave susceptor interferences. Therefore, MAP provided a rapid, safe, and efficient means of depolymerizing biomass, thus holding promise for biorefinery applications.

Special Prey, Special Glue: NMR Spectroscopy on Aggregate Glue Components of Moth-Specialist Spiders, Cyrtarachninae.

Orb-weaver spiders produce upwards of seven different types of silk, each with unique material properties. We focus on the adhesive within orb-weaving spider webs, aggregate glue silk. These droplets are composed of three main components: water, glycoproteins, and a wide range of low molecular mass compounds (LMMCs). These LMMCs are known to play a crucial role in maintaining the material properties of the glycoproteins, aid in water absorption from the environment, and increase surface adhesion. Orb-weavers within the Cyrtarachninae subfamily are moth specialists and have evolved glue droplets with novel material properties. This study investigated the biochemical composition and diversity of the LMMCs present in the aggregate glue of eight moth-specialist species and compared them with five generalist orb-weavers using nuclear magnetic resonance (NMR) spectroscopy. We hypothesized that the novel drying ability of moth-specialist glue was accompanied by novel LMMCs and lower overall percentages by silk weight of LMMCs. We measured no difference in LMMC weight by the type of prey specialization, but observed novel compositions in the glue of all eight moth-catching species. Further, we quantified the presence of a previously reported but unidentified compound that appears in the glue of all moth specialists. These silks can provide insight into the functions of bioadhesives and inform our own synthetic adhesives.

Development and evaluation of a gas chromatography-mass spectrometry method for biogenic amines to assess decomposition in seafood

Biogenic amines (BAs) are low molecular mass compounds formed by the microbial-induced decarboxylation of specific amino acids. These molecules are markers of quality index and can indicate potential spoilage of a product. Currently, the FDA relies on sensory analysis as well as indole and histamine levels to evaluate the degree of seafood decomposition. However, there is a need for alternative analytical methods to corroborate those analyses. An optimized dispersive liquid-liquid microextraction (DLLME) method was developed for the extraction of four BAs (putrescine, cadaverine, histamine and tyramine) from various decomposition stages of nine seafood species previously tested by the FDA Seafood Sensory Experts. The BAs depicted very different concentration patterns between species and were able to distinguish within-species decomposition stages classified by the organoleptic analysis as “borderline increments”. The results suggest that all four analyzed BAs can be potentially used as biomarkers of seafood decomposition, but the choice of biomarker is species dependent. Some of the prominent associations were putrescine in shrimp, cadaverine in weakfish, histamine in canned tuna, and tyramine in scallops. The differentiation between “borderline” stages of decomposition also demonstrates the suitability of the method to support the FDA sensory analyses of seafood, ultimately leading to improved consumer protection.

Targeting the YAP/TAZ mechanotransducers in solid tumour therapeutics.

Targeting the YAP/TAZ mechanotransducers in solid tumour therapeutics.

Mechanisms and solutions for nasal drug delivery - a narrative review.

The aim of this paper is to review mechanisms and solutions for nasal drug delivery. Literature survey was performed via PubMed, Google Scholar, Google, and ProQuest Central database of Kirikkale University. The nasal lining presents a large area of endothelium of variable permeability and with a rich vascular supply. Advantages of this route include eliminating first-pass metabolism and being easily accessible. The nasal route enables some agents which are otherwise difficult to administer to enter the systemic circulation, for example, low molecular mass compounds with high polarity, peptides, or proteins. There are three principal factors that influence the extent to which drugs can be absorbed through the nasal lining, namely the physico-chemical characteristics of the drug molecule itself, the action of the mucociliary system within the nose, and the presence of any factors increasing nasal absorption. A key factor limiting the use of the intranasal route of administration is insufficient absorption through the nasal mucosa. A number of drugs in development cannot be administered intranasally because their bioavailability following nasal administration is too low. There has been considerable research focus on methods to enhance absorption via the nasal mucosa. In this chapter, we review the literature related to this problem and discuss potential solutions.

Biochemical and Toxinological Characterization of Venom from Macrorhynchia philippina (Cnidaria, Hydrozoa)

Macrorhynchia philippina is a colonial benthic hydroid from the Class Hydrozoa (Phylum Cnidaria) distributed in the tropical and subtropical marine waters from Atlantic Ocean, Indo-Pacific, and Mozambique. Its colonies somewhat resemble plants, causing confusion in the bathers who accidentally touch the animal. Acute burning/local pain, edema, erythema, and pruritus were symptoms already described, but its venom composition is unknown, as well as the participation of toxins for the symptom's development. Thus, herein, we show the biochemical composition and toxic effects of M. philippina venom. Colonies were collected and processed for histological analysis; alternatively, they were immersed into methanol containing 0.1% acetic acid for venom attainment, which was analyzed by mass spectrometry and submitted to edema and nociception evaluation in mice, hemolysis and antimicrobial assays in vitro. Before the molecule's extraction, it was possible to see the inoculation structures (hydrocladiums and hydrotheca) containing venom, which was released after the immersion of the animal in the solvents. The venom was composed mainly by low molecular mass compounds, able to cause significant reduction of the paw withdrawal latency from the hot plate test, 30 minutes after the injection. Moreover, significant edema was observed 10 and 30 minutes after the injection, indicating the activity of at least two inflammatory mediators. The venom caused no hemolytic activity but reduced the growth of A. baumannii and K. pneumoniae strains. This study is the first biochemical description of M. philippina venom, with molecules that cause fast inflammatory and painful effects, characteristic of the envenomation.

Characterization of a Novel Protease Inhibitor from the Edible Mushroom Agaricus bisporus.

Protease inhibitors inhibit the activity of protease enzymes; hence, they are essentially involved in the regulation of the metabolic processes involving protease enzymes and the protection of the host organism against external damage due to proteases. These inhibitors are abundantly present in all living organisms but have not been much reported in mushrooms. Mushrooms are one of the major food components of humans, with delicious taste and high nutritional value. Mushrooms also have therapeutic and economic significance. The edible mushrooms with medicinal properties are much in commercial demand. To date, the presence of protease inhibitors has not been reported much in edible mushrooms. The present study reports the characterization of a protease inhibitor isolated from the common white button mushroom Agaricus bisporus. The objective of the present study is to characterize the novel protease inhibitor from Agaricus bisporus in order to determine its nature and activity under varying environmental conditions. The protease inhibitor was characterized through SDS PAGE, gel filtration chromatography, and de novo sequencing in order to determine its molecular mass and sequence, respectively. The optimum pH, temperature, and thermal stability were studied to determine the optimum working range of the protease inhibitor. The protease inhibitory activity (%) was determined in the presence of metal ions, surfactants, oxidizing agents, and reducing agents. The kinetic parameters and the type of inhibition exhibited by the protease inhibitor were determined using casein and trypsin protease enzyme. The protease inhibitor was found to be a low molecular mass compound of 25 kDa. The de novo sequencing matched the inhibitor against a 227 amino acid containing peptide molecular mass of 24.6 kDa molecular mass. The protease inhibitory activity (%) was found highest at pH 7.0 and temperature 50 °C, and the inhibitor was stable from pH 4.0-9.0 and temperature 30-80 °C. In the presence of metal ions, the residual protease inhibitory activity (%) enhanced in the presence of Na+, Mg2+, and Fe3+. The residual activity increased in the presence of the surfactant SDS slightly in comparison to control, while it decreased in the case of Triton-X and Tween 20. The presence of oxidizing agents, hydrogen peroxide and dimethyl sulfoxide decreased the residual inhibitory activity. The protease inhibitor's activity was unaffected by the reducing agents, dithiothreitol and β-mercaptoethanol, at up to 2mM concentration, but it decreased at higher concentrations. The inhibitor exhibited uncompetitive inhibition against trypsin with an inhibitory constant of 166 nM, indicating a strong affinity towards the protease, with a half-life of 93.90 minutes at 37 °C. Protease inhibitors isolated from mushrooms are generally small in size, more stable, and tolerant towards varying external conditions. The protease inhibitor isolated from Agaricus bisporus also exhibited similar characteristics.

Advanced characterization of oxidized derivatives in alternative fatty esters mixture for biodiesel purposes

Biofuels from unconventional sources contribute to the reduction of environmental impacts without competing with the food market. Samples of fatty esters mixture (FEM) for biodiesel purposes were produced from conventional and alternatives feedstocks sources of triacylglycerols (TAG). In this work, we evaluated the oxidative stability through a complex and advanced characterization at the molecular level of the chemical changes that occurred in these samples for a storage period of 2.5 years. Esters contents were determined by both TG and GC-FID analyses, and values with relative errors from 0.36 to 23.28% were obtained. Low molecular mass compounds derived from the oxidative processes and free fatty acids (FFA) contribute to these differences. TG curves also showed the presence of contaminants with high thermal stability, which were characterized by EASI(+)-MS. TAG and diacylglycerol (DAG) were identified, however, dimers and theirs derived from hydroperoxide degradation were detected as major contaminants, confirmed by the presence of biomarkers ions characteristics of dimers. Our work mapping and presenting the chemical profile of oxidative products of FEM, and in addition, we propose the correlation of relative abundance of ion m/z 349 corresponding to the hydroperoxide [C18:2 + 2O + Na]+ with the peroxide index values.

Box Jellyfish (Cnidaria, Cubozoa) Extract Increases Neuron's Connection: A Possible Neuroprotector Effect.

Neurodegenerative diseases are one of the major causes of death worldwide, characterized by neurite atrophy, neuron apoptosis, and synapse loss. No effective treatment has been indicated for such diseases so far, and the search for new drugs is being increased in the last years. Animal venoms' secretion/venom can be an alternative for the discovery of new molecules, which could be the prototype for a new treatment. Here, we present the biochemical characterization and activity of the extract from the box jellyfish Chiropsalmus quadrumanus (Cq) on neurites. The Cq methanolic extract was obtained and incubated to human SH-SY5Y neurons, and neurite parameters were evaluated. The extract was tested in other cell types to check its cytotoxicity and was submitted to biochemical analysis by mass spectrometry in order to check its composition. We could verify that the Cq extract increased neurite outgrowth length and branching junctions, amplifying the contact between SH-SY5Y neurons, without affecting cell body and viability. The extract action was selective for neurons, as it did not cause any effects on other cell types, such as tumor line, nontumor line, and red blood cells. Moreover, mass spectrometry analysis revealed that there are no proteins but several low molecular mass compounds and peptides. Three peptides, characterized as cryptides, and 14 low molecular mass compounds were found to be related to cytoskeleton reorganization, cell membrane expansion, and antioxidant/neuroprotective activity, which act together to increase neuritogenesis. After this evaluation, we conclude that the Cq extract is a promising tool for neuronal connection recovery, an essential condition for the treatment of neurodegenerative diseases.

MS/MS analysis of four scorpion venoms from Colombia: a descriptive approach.

Background: Scorpions are widely known for the neurotoxic effects of their venoms, which contain peptides affecting ionic channels. Although Colombia is recognized for its scorpion diversity, only a few studies are available describing the venom content. Methods: In this descriptive study, we analyzed the MS/MS sequence, electrophoretic and chromatographic profile linked to a bioinformatics analysis of the scorpions Chactas reticulatus (Chactidae), Opisthacanthus elatus (Hormuridae), Centruroides edwardsii (Buthidae) and Tityus asthenes (Buthidae) from Colombia. Results: Each scorpion showed a specific electrophoretic and chromatographic profile. The electrophoretic profiles indicate the presence of high molecular mass compounds in all venoms, with a predominance of low molecular mass compounds in the Buthidae species. Chromatographic profiles showed a similar pattern as the electrophoretic profiles. From the MS/MS analysis of the chromatographic collected fractions, we obtained internal peptide sequences corresponding to proteins reported in scorpions from the respective family of the analyzed samples. Some of these proteins correspond to neurotoxins affecting ionic channels, antimicrobial peptides and metalloproteinase-like fragments. In the venom of Tityus asthenes, the MSn analysis allowed the detection of two toxins affecting sodium channels covering 50% and 84% of the sequence respectively, showing 100% sequence similarity. Two sequences from Tityus asthenes showed sequence similarity with a phospholipase from Opisthacanthus cayaporum indicating the presence of this type of toxin in this species for the first time. One sequence matching a hypothetical secreted protein from Hottentotta judaicus was found in three of the studied venoms. We found that this protein is common in the Buthidae family whereas it has been reported in other families - such as Scorpionidae - and may be part of the evolutionary puzzle of venoms in these arachnids. Conclusion: Buthidae venoms from Colombia can be considered an important source of peptides similar to toxins affecting ionic channels. An interesting predicted antimicrobial peptide was detected in three of the analyzed venoms.

Ethylene Induction of Non-Enzymatic Metabolic Antioxidants in Matricaria chamomilla.

Phytochemical investigations of Matricaria chamomilla L. (Asteraceae) stated the presence of several compounds with an established therapeutic and antioxidant potential. The chamomile non-enzymatic antioxidant system includes low molecular mass compounds, mainly polyphenols such as cinnamic, hydroxybenzoic and chlorogenic acids, flavonoids and coumarins. The objective of this work was to evaluate the role of the non-enzymatic antioxidant system after stimulation by ethylene in tetraploid chamomile plants. Seven days of ethylene treatment significantly increased the activity of phenylalanine ammonia-lyase, which influenced the biosynthesis of protective polyphenols in the first step of their biosynthetic pathway. Subsequently, considerable enhanced levels of phenolic metabolites with a substantial antioxidant effect (syringic, vanillic and caffeic acid, 1,5-dicaffeoylquinic acid, quercetin, luteolin, daphnin, and herniarin) were determined by HPLC-DAD-MS. The minimal information on the chlorogenic acids function in chamomile led to the isolation and identification of 5-O-feruloylquinic acid. It is accumulated during normal conditions, but after the excessive effect of abiotic stress, its level significantly decreases and levels of other caffeoylquinic acids enhance. Our results suggest that ethephon may act as a stimulant of the production of pharmaceutically important non-enzymatic antioxidants in chamomile leaves and thus, lead to an overall change in phytochemical content and therapeutic effects of chamomile plants, as well.

Analysis the water in aggregate glue droplets of spider orb web by TOF‐SIMS

Orb‐weaver spiders of the family Araneidae produce a viscous glue from aggregate glands. Spiders effectively capture prey by coating the viscous glue onto the spiral lines. The viscous glue has an unusual property. The main components are glycoproteins, salts (low molecular mass compounds [LMMCs] and inorganic salt), and water. The interaction of water and glycoproteins relies on the presence of salts. Here, we used a freeze method to analyze the behavior of water of the viscous glue using time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). We found that the matrix effect of glycoprotein may cause ion suppression of water in aggregate glue droplets. Moreover, the changes in element distribution before and after the viscous glue adheres to the object suggest that after losing salts, water not only ceases to interact with glycoproteins but also oozes with the salts.

Fouling Analysis and the Recovery of Phytosterols from Orange Juice Using Regenerated Cellulose Ultrafiltration Membranes

This study describes the use of regenerated cellulose (RCA) membranes with molecular weight cut-off (MWCO) values of 10, 30, and 100 kDa, respectively, to separate phytosterols from orange juice for possible nutraceutical production. A desirable membrane separation rejects protein whilst transmitting phytosterols and other low molecular mass compounds such as sugars. The ultrafiltration was performed in a cross-flow membrane system with a total filtration area of 336 cm2. Total phytosterol analysis was carried out by using a Liebermann-Buchard-based method. Protein concentration was quantified by the Bradford method. The effects of three different membranes upon the rejection of total phytosterol content, proteins, sugar, and antioxidant activity were studied. Of the membranes tested, the 10-kDa membrane displayed the highest concentration of phytosterols in the permeate. The 30-kDa and 100-kDa membranes gave comparatively higher phytosterol rejection. The membrane surface roughness and corresponding pure water flux values varied as a function of MWCO such that RCA30 > RCA100 > RCA10. Membranes with rougher surfaces displayed higher fouling than those with smoother surfaces. Hydrophobicity and surface roughness both influenced filtration performance, by controlling the development of the protein-based foulant which modified membrane selectivity.

Electrospray: More than just an ionization source.

Electrospraying (ES) is a potential-driven process of liquid atomization, which is employed in the field of analytical chemistry, particularly as an ionization technique for mass spectrometric analyses of biomolecules. In this review, we demonstrate the extraordinary versatility of the electrospray by overviewing the specifics and advanced applications of ES-based processing of low molecular mass compounds, biomolecules, polymers, nanoparticles, and cells. Thus, under suitable experimental conditions, ES can be used as a powerful tool for highly controlled deposition of homogeneous films or various patterns, which may sometimes even be organized into 3D structures. We also emphasize its capacity to produce composite materials including encapsulation systems and polymeric fibers. Further, we present several other, less common ES-based applications. This review provides an insight into the remarkable potential of ES, which can be very useful in the designing of innovative and unique strategies.

Gold Nanoparticle-Assisted Black Silicon Substrates for Mass Spectrometry Imaging Applications.

Mass spectrometry imaging (MSI) based on matrix-assisted laser desorption ionization (MALDI) is widely used in proteomics. However, matrix-free technologies are gaining popularity for detecting low molecular mass compounds. Small molecules were analyzed with nanostructured materials as ionization promoters, which produce low-to-no background signal, and facilitate enhanced specificity and sensitivity through functionalization. We investigated the fabrication and the use of black silicon and gold-coated black silicon substrates for surface-assisted laser desorption/ionization mass spectrometry imaging (SALDI-MSI) of animal tissues and human fingerprints. Black silicon was created using dry etching, while gold nanoparticles were deposited by sputtering. Both methods are safe for the user. Physicochemical characterization and MSI measurements revealed the optimal properties of the substrates for SALDI applications. The gold-coated black silicon worked considerably better than black silicon as the LDI-MSI substrate. The substrate was also compatible with imprinting, as a sample-simplification method that allows efficient transference of metabolites from the tissues to the substrate surface, without compound delocalization. Moreover, by modifying the surface with hydrophilic and hydrophobic groups, specific interactions were stimulated between surface and sample, leading to a selective analysis of molecules. Thus, our substrate facilitates targeted and/or untargeted in situ metabolomics studies for various fields such as clinical, environmental, forensics, and pharmaceutical research.

Elucidation of the Structure and Synthesis of Neuroprotective Low Molecular Mass Components of the Parawixia bistriata Spider Venom.

The South American social spider Parawixia bistriata produces a venom containing complex organic compounds with intriguing biological activities. The crude venom leads to paralysis in termites and stimulates l-glutamate uptake and inhibits GABA uptake in rat brain synaptosomes. Glutamate is the major neurotransmitter at the insect neuromuscular junction and at the mammalian central nervous system, suggesting a modulation of the glutamatergic system by the venom. Parawixin1, 2, and 10 (Pwx1, 2 and 10) are HPLC fractions that demonstrate this bioactivity. Pwx1 stimulates l-glutamate uptake through the main transporter in the brain, EAAT2, and is neuroprotective in in vivo glaucoma models. Pxw2 inhibits GABA and glycine uptake in synaptosomes and inhibits seizures and neurodegeneration, and Pwx10 increases l-glutamate uptake in synaptosomes and is neuroprotective and anticonvulsant, shown in in vivo epilepsy models. Herein, we investigated the low molecular mass compounds in this venom and have found over 20 small compounds and 36 unique acylpolyamines with and without amino acid linkers. The active substances in fractions Pwx1 and Pwx2 require further investigation. We elucidated and confirmed the structure of the active acylpolyamine in Pwx10. Both fraction Pwx10 and the synthesized component enhance the activity of transporters EAAT1 and EAAT2, and, importantly, offer in vitro neuroprotection against excitotoxicity in primary cultures. These data suggest that compounds with this mechanism could be developed into therapies for disorders in which l-glutamate excitotoxicity is involved.

Enzymatic transformation of aflatoxin B1 by Rh_DypB peroxidase and characterization of the reaction products

In some environments, a number of crops, notably maize and nuts can be contaminated by aflatoxin B1 and related compounds resulting from the growth of aflatoxin-producing Aspergilli. Fungal peroxidases have been shown to degrade a number of mycotoxins, including aflatoxin B1 (AFB1). Therefore, the purpose of this study was to investigate the in vitro enzymatic degradation AFB1 by a recombinant type B dye decolorizing peroxidase (Rh_DypB). Analysis of the reaction products by HPLC-MS analysis showed that under optimized conditions AFB1 was efficiently transformed by Rh_DypB, reaching a maximum of 96% conversion after 4 days of reaction at 25 °C. Based on high resolution mass spectrometry analysis, AFB1 was demonstrated to be quantitatively converted to AFQ1, a compound with a significantly lower toxicity. A number of low molecular mass compounds were also present in the final reaction mixture in small quantities. The results presented in this study are promising for a possible application of the enzyme Rh_DypB for aflatoxin reduction in feed.

Application of linear solvation energy relationships and principal component analysis methods for the prediction of the retention behaviour of E-resveratrol analogues with substituted silica hydride stationary phases

In this investigation, application of linear solvent energy relationships (LSERs) and principal component analysis (PCA) methods have been employed to investigate the structure-retention dependencies of E-resveratrol analogues separated under different stationary and mobile phase conditions. To this end, the retention of 22 analogues have been determined with phenyl, diol, bidentate anchored C18 (BDC18) and Diamond Hydride™ C18 (DHC18) substituted silica hydride stationary phases under isocratic chromatographic conditions using mobile phases containing 0.1 (% v/v) formic acid and different acetonitrile or methanol contents from 10 to 90% (v/v) in 10% increments. In general, these compounds showed decreasing retention with increased acetonitrile or methanol content in the mobile phase with all the stationary phases. The retention order generally followed their log P values, although some unique selectivity variations were apparent depending on the nature of the selected stationary and mobile phases. These 22 compounds contained different backbone functionalities linking the phenyl ring A to phenyl ring B and different numbers of hydroxyl groups in the phenyl ring A/phenyl ring B. Structure-retention descriptors, derived according to LSER concepts, were analysed by PCA methods to provide group classification of these resveratrol analogues from the associated PC1 versus PC2 score plots. These results revealed that the selectivity of these compounds was dominated by hydrophobic and steric interactions. Based on the number and position of hydroxyl groups in a specific resveratrol analogue, a reliable curve fitting approach (indicated by R2 > 0.99 for the correlation between experimental and predicted log k values) was derived for prediction of the retention of these analytes under different mobile phase isocratic separation conditions. The application of similar methods are anticipated to find general utility for the analysis of diverse classes of other low molecular mass compounds in the different modes of liquid chromatography, permitting enhanced levels of prediction and evaluation of the retention attributes of polar and non-polar compounds.

Recent advances in nanostructure/nanomaterial-assisted laser desorption/ionization mass spectrometry of low molecular mass compounds

Laser desorption ionization mass spectrometry (LDI-MS) has been developed to be an essential tool for the analysis and identification of a large variety of species, ranging from small metabolites, drugs and pollutants to peptides and proteins and even to bacteria. Matrix assisted LDI-MS has shown a great power for macromolecules, but its analytical capability to low mass compounds is limited due to inherent drawbacks, including abundant interference in low mass range (<800 Da) caused by matrix self-dissociation and poor reproducibility due to inhomogeneous crystallization. Several matrix-free methods have been developed to solve these issues, mainly through altering organic matrix with inorganic nanostructured surfaces or nanomaterials as LDI medium. In the past five years, improvements on conventional silicon-based, metal-based, metal oxide-based and carbon-based LDI media as well as emerging novel materials such as 2D nanomaterials and organic frameworks have gained important progresses. Meanwhile, with the deep research in light-matter interaction, LDI mechanism studies begin to grow and become to attach great importance. Advances in both medium and mechanism promote to expand the applicable potential of nanostructure/nanomaterial-assisted LDI-MS in many aspects, including trace analysis, structural analysis and MS imaging. In this review, we survey the major progresses in this area in recent years. We also sketch remaining challenges and directions for future development.

Membrane Separation of the Base-Catalyzed Depolymerization of Black Liquor Retentate for Low-Molecular-Mass Compound Production.

One way of valorizing the lignin waste stream from the pulp and paper industries is depolymerizing it into low-molecular-mass compounds (LMMC). However, a common problem in the depolymerization of Kraft lignin is the low yields of small aromatic molecules obtained. In the present work, the combination of the repeated depolymerization of lignin and the separation of LMMC from depolymerized lignin to upgrade them into value-added chemicals was studied. In so doing, we investigated the possibility of depolymerizing black liquor retentate (BLR). The base-catalyzed depolymerization of BLR was performed using a continuous flow reactor at 170–210 °C, with a 2 min residence time. The results obtained indicate that BLR can be depolymerized effectively under the experimental conditions. Depolymerized lignin LMMC can be successfully separated by a GR95PP membrane, and thus be protected from repolymerization. Through combining membrane filtration with base-catalyzed depolymerization, more than half of the lignin could be depolymerized into LMMC. Around 46 mg/g of lignin monomers (guaiacol, vanillin, acetovanillone, and acetosyringone), which can potentially be upgraded to high-valued chemicals, were produced. On the basis of our results, we suggest use of a recycling Kraft lignin depolymerization and filtration process for maximizing the production of LMMC under mild alkaline conditions.