Type Of Linkage Research Articles

Chemometric Combination of Ultrahigh Resolving Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy for a Structural Characterization of Lignin Compounds.

In recent years, the potential of lignins as a resource for material-based applications has been highlighted in many scientific and nonscientific publications. But still, to date, a lack of detailed structural knowledge about this ultracomplex biopolymer undermines its great potential. The chemical complexity of lignin demands a combination of different, powerful analytical methods, in order to obtain these necessary information. In this paper, we demonstrate a multispectroscopic approach using liquid-state and solid-state Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and nuclear magnetic resonance (NMR) spectroscopy to characterize a fractionated LignoBoost lignin. Individual FT-ICR-MS, tandem MS, and NMR results helped to determine relevant information about the different lignin fractions, such as molecular weight distributions, oligomer sizes, linkage types, and presence of specific functional groups. In addition, a hetero spectroscopic correlation approach was applied to chemometrically combine MS, MS/MS, and NMR data sets. From these correlation analyses, it became obvious that a combination of tandem MS and NMR data sets gives the opportunity to comprehensively study and describe the general structure of complex biopolymer samples. Compound-specific structural information are obtainable, if this correlation approach is extended to 1D-MS and NMR data, as specific functional groups or linkages are verifiable for a defined molecular formula. This enables structural characterization of individual lignin compounds without the necessity for tandem MS experiments. Hence, these correlation results significantly improve the depth of information of each individual analysis and will hopefully help to structurally elucidate entire lignin structures in the near future.

Ultrasonic extraction of Moringa oleifera seeds polysaccharides: Optimization, purification, and anti-inflammatory activities

Natural polysaccharides exhibit numerous beneficial properties, such as antioxidant, antitumor, hypoglycemic, and hypolipidemic activities. Moringa oleifera seeds are of high dietary and therapeutic value which drew a lot of attention. However, the regulation effect on anti-inflammatory activity of polysaccharides remains to be studied. Herein, novel bioactive polysaccharides (MOSP-1) were extracted from Moringa oleifera seeds, and the anti-inflammatory properties of MOSP-1 were uncovered. Ultrasound-assisted extraction (UAE) was used to prepare the polysaccharides with optimized conditions (70 °C, 43 min, and liquid-solid-ratio 15 mL/g). Then, DEAE-Sepharose Fast Flow columns were applied to isolate and purify MOSP-1. Rhamnose, arabinose, galactose, and glucose were identified as the monosaccharide constituents of MOSP-1, with a molecular weight of 5.697 kDa. Their proportion in molarity was 1:0.183:0.108:0.860 and 8 types of glycosidic linkages were discovered. Bioactive assays showed that MOSP-1 possessed scavenging activities against DPPH and ABTS radicals, confirming its potential antioxidation efficacy. In vitro experiments revealed that MOSP-1 could reduce the expression of inflammation-related cytokines, inhibit the activation of ERK, JNK, and p38 (the MAPK signaling pathway), and enhance phagocytic functions. This study indicates that polysaccharides (MOSP-1) from Moringa oleifera seeds with anti-inflammatory properties may be used for functional food and pharmaceutical product development.

ASCA-related antibodies in the blood sera of healthy donors and patients with colorectal cancer: characterization with oligosaccharides related to Saccharomyces cerevisiae mannan.

Mannans are polysaccharide antigens expressed on the cell wall of different fungal species including Saccharomyces cerevisiae and Candida spp. These fungi are components of the normal intestinal microflora, and the presence of antibodies to fungal antigens is known to reflect the features of the patient's immune system. Thus, titers of IgG and IgA antibodies against Saccharomyces cerevisiae mannan (ASCA) are markers for clinical diagnostics of inflammatory bowel diseases. The complex organization and heterogeneity of cell-wall mannans may reduce the quality and reproducibility of ELISA results due to interference by different antigenic epitopes. In this research, we analyzed the levels of IgG antibodies in the sera of healthy donors and patients with colorectal cancer using an array of synthetic oligosaccharides related to distinct fragments of fungal mannan. This study aimed to establish the influence of oligosaccharide structure on their antigenicity. Variations in the structure of the previously established ASCA epitope (changing type of linkage, chain length, and the presence of branches) significantly modified the ability of ligands to bind to circulating antibodies in blood sera. The study showed that surface presentation density of the ligand critically affects the results of enzyme immunoassay. The transition from natural coating antigens to their corresponding synthetic mimetics with a defined structure opens new opportunities for improving existing ELISA test systems, as well as developing diagnostic kits with new properties.

Altered Rheological Properties of Insoluble α-Glucan, Synthesized by Mutant Glucansucrase U13M1

Lactic acid bacteria from the Leuconostoc, Lactobacillus, and Streptococcus genera produce en¬zymes from the glucoside hydrolase family 70 (GH70) that synthesize α-D-glucans with various types of linkages and degrees of branching. These polymers with novel physico-chemical properties are an object of great interest for expanding application in the food, pharmaceutical, and cosmetic industries. Using site-directed mutagenesis, a mutant variant of glucansucrase URE 13-300 was obtained. The enzyme ex¬pression of the modified enzyme was optimized and the rheological properties of both types of glucans were evaluated. The modified insoluble glucan, synthesized by mutant glucansucrase U13M1 exhibited significantly higher apparent viscosity at 8°C – 3550 mPa.s at a shear rate of 0.2 s-1 than the original glucan. Higher temperatures up to 80°C had a moderate influence on the viscosity as well. The presented findings are a good precondition for further exploration of modified insoluble glucans for industrial application.

Inhomogeneities of sulfidic linkages and mullins effect in isoprene rubber vulcanizates vulcanized with sulfur donor agents

Gum vulcanizates exhibit the Mullins effect during large-strain cyclic tension. However, the details of the Mullins effect remain unclarified due to the difficulty of analysis of a complicated network structure. The Mullins effect in isoprene rubber (IR) vulcanizates has been systematically investigated to clarify the impacts of network inhomogeneities caused by the distribution of sulfidic linkages. Chemical probe experiments and paraffin swelling have been performed in an attempt to clarify the contribution of the presence of different types of sulfidic linkages. Thermo-oxidative aging at a moderate temperature (353 K) has been used to assess the effect of changes in structural inhomogeneity on the Mullins effect in aged vulcanizates. During cyclic tension deformations, the recovery hysteresis and accumulated softening energy densities normalized by theoretical shear modulus of elastically effective network are influenced by the heterogeneity of network structure only before the onset of crystallization. These findings can be used to inform the design of the network structure and enhance the performance of rubber products.

β-arrestin1 is an E3 ubiquitin ligase adaptor for substrate linear polyubiquitination

G protein-coupled receptor (GPCR) signaling and trafficking are regulated by multiple mechanisms, including posttranslational modifications such as ubiquitination by E3 ubiquitin ligases. E3 ligases have been linked to agonist-stimulated ubiquitination of GPCRs via simultaneous binding to βarrestins. In addition, βarrestins have been suggested to assist E3 ligases for ubiquitination of key effector molecules, yet mechanistic insight is lacking. Here, we developed an invitro reconstituted system and show that βarrestin1 (βarr1) serves as an adaptor between the effector protein signal-transducing adaptor molecule 1 (STAM1) and the E3 ligase atrophin-interacting protein 4. Via mass spectrometry, we identified seven lysine residues within STAM1 that are ubiquitinated and several types of ubiquitin linkages. We provide evidence that βarr1 facilitates the formation of linear polyubiquitin chains at lysine residue 136 on STAM1. This lysine residue is important for stabilizing the βarr1:STAM1 interaction in cells following GPCR activation. Our study identifies atrophin-interacting protein 4 as only the second E3 ligase known to conjugate linear polyubiquitin chains and a possible role for linear ubiquitin chains in GPCR signaling and trafficking.

Oligo(phenylenevinylene)-Based Covalent Organic Frameworks with Kagome Lattice for Boosting Photocatalytic Hydrogen Evolution.

Covalent organic frameworks (COFs) have shown great advantages as photocatalysts for hydrogen evolution. However, the effect of linkage geometry and type of linkage on the extent of π-electron conjugation in the plane of the framework and photocatalytic properties of COFs remains a significant challenge. Herein, two Kagome (kgm) topologic oligo(phenylenevinylene)-based COFs are designed and synthesized for boosting photocatalytic hydrogen evolution via a "two in one" strategy. Under visible light irradiation, COF-954 with 5 wt% Pt as cocatalyst exhibits high hydrogen evolution rate (HER) of 137.23mmol g-1 h-1 , outperforming most reported COF-based photocatalysts. More importantly, even in natural seawater, COF-954 shows an average HER of 191.70mmol g-1 h-1 under ultraviolet-visible (UV-vis) light irradiation. Additionally, the water-drainage experiments indoors and outdoors demonstrate that 25 and 8mL hydrogen gas could be produced in 80 min under UV-vis light and natural sunlight, respectively, corresponding to a high HER of 167.41 and 53.57mmol h-1 g-1 . This work not only demonstrates an effective design strategy toward highly efficient COF-based photocatalysts, but also shows the great potential of using the COF-based photocatalysts for photocatalytic hydrogen evolution.

Structural characterization of a polysaccharide derived from Saposhnikovia divaricatee (Turcz.) Schischk with anti-allergic and antioxidant activities

Ethnopharmacological relevanceSaposhnikoviae Radix, the dry root of Saposhnikovia divaricatee (Turcz.) Schischk, is a traditional chinese medicine used for the treatment of cold, headache, and skin pruritus. Aim of the studyThis study aimed to identify novel active polysaccharides from Saposhnikovia divaricatee (Turcz.) Schischk and clarify their structures and bioactivities. Materials and methodsThe structure of polysaccharides was clarified by PMP-HPLC, methylation analysis, particle acid hydrolysis analysis and NMR analysis. The anti-allergic and antioxidant activities of polysaccharides were evaluated on allergic reaction model in RBL-2H3 cells and oxidative damage model of C. elegans. ResultsWe purified a novel homogenous polysaccharide named SP-3 from Saposhnikovia divaricatee (Turcz.) Schischk and its molecular weight was determined as 3.096 × 104 Da. Monosaccharide composition analysis revealed that SP-3 was composed of mannose, rhamnose, galacturonic acid, glucose, galactose, and arabinose (1.85: 5.22: 38.06: 2.36: 23.25: 29.26). The main linkage type of SP-3 was a repeat unit of →4,6)-β-D-Galp-(1 → 4)-α-D-GalpA-(1 → . The branches of SP-3 contained T-linked-α-L-Araf and 1,3,4-linked-α-L-Rhap. It was observed that SP-3 inhibited β-HEX release and inflammatory factors in RBL-2H3 cells subject to IgE stimulant. Meanwhile, SP-3 increased the mean lifespan of Caenorhabditis elegans under oxidative stress, reduced ROS content and increased antioxidant enzyme activities of C. elegans, potentially through activating the SOD-3. ConclusionsA novel homogenous polysaccharide was identified from Saposhnikovia divaricatee (Turcz.) Schischk, and this polysaccharide SP-3 played key roles for the anti-allergic and antioxidant activities.

Structural characterization and immunomodulatory activity of an acidic polysaccharide from walnut green husk

Acidic walnut green husk polysaccharide with weight average molecular weight of 5.101 kDa was isolated and designated WGHP-2, which was composed of galacturonic acid (69.47 %), galactose (11.18 %), rhamnose (8.67 %), arabinose (3.96 %), glucose (2.21 %), glucuronic acid (2.28 %), xylose (0.83 %), fucose (0.81 %) and mannose (0.59 %). The main glycosidic linkage types of WGHP-2 were → 4-α-D-Glcp-(1→, →4-α-D-GalpA-(1→, t-β-D-GlcpA-(1→, →2-β-D-Rhap-(1→, t-α-D-Galp-(1→, →4-α-D-Galp-(1 → and → 2,4)-α-D-Manp(1 →. Immunostimulating assays showed that WGHP-2 could significantly promote the proliferation of RAW264.7 cells, strengthen the phagocytic activity, and up-regulate the production and release of NO, ROS, TNF-α, INF-β and IL-6. Western-blot analysis indicated that MAPK and PI3K/Akt pathways were involved in the activation of macrophages induced by WGHP-2. Overall, our study suggests that WGHP-2 has the potential to be developed as a functional food with good immunostimulatory activity.

Deubiquitylating Enzymes in Cancer and Immunity.

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Sialic acid O-acetylation patterns and glycosidic linkage type determination by ion mobility-mass spectrometry

O-acetylation is a common modification of sialic acids that has been implicated in a multitude of biological and disease processes. A lack of analytical methods that can determine exact structures of sialic acid variants is a hurdle to determine roles of distinct O-acetylated sialosides. Here, we describe a drift tube ion mobility-mass spectrometry approach that can elucidate exact O-acetylation patterns as well as glycosidic linkage types of sialosides isolated from complex biological samples. It is based on the use of a library of synthetic O-acetylated sialosides to establish intrinsic collision cross section (CCS) values of diagnostic fragment ions. The CCS values were used to characterize O-acetylated sialosides from mucins and N-linked glycans from biologicals as well as equine tracheal and nasal tissues. It uncovered contrasting sialic acid linkage types of acetylated and non-acetylated sialic acids and provided a rationale for sialic acid binding preferences of equine H7 influenza A viruses.

Isolation, characterization, trypsin inhibition, liver protective and antioxidant activities of arabinoxylan from Massa Medicata Fermentata and its processed products

Massa Medicata Fermentata (MMF) is a traditional Chinese medicine widely used in feed additives and human medicine. In this study, two neutral polysaccharides (SMMFP-1 and CMMFP-1) were isolated from two forms of MMF (sheng and chao MMF), and their structural characteristics and bioactivities were studied. The results showed that CMMFP-1 had higher average Mw compared with that of SMMFP-1. SMMFP-1 had a lower proportion of Ara, Xyl, GalA, and GlcA, but higher levels of Fuc, Gal, Man, and GulA. Compared with CMMFP-1, SMMFP-1 had a triple helix structure. SMMFP-1 had a layered structure, whereas CMMFP-1 had a curly layered structure. More glycosidic linkage types were found in SMMFP-1 than in CMMFP-1, and SMMFP-1 had a greater number of side chains. More importantly, SMMFP-1 showed better trypsin inhibition activity in vitro, liver-protective activity in vivo, and stronger antioxidant activity in vivo than CMMFP-1. Thus, arabinoxylans may be one of the active substances for different efficacies between MMF and its processed product. The results of this study facilitate the exploration of the correlation between the structural characteristics and biological functionalities of MMF arabinoxylans. Moreover, a theoretical basis is established for further study of the unique properties of arabinoxylans and their applications.

Structural characterization of a low-molecular-weight polysaccharide from Plumula Nelumbinis and evaluation of its antioxidant and anti-inflammatory activity

Plumula Nelumbinis polysaccharides (PNP) exhibit remarkable bioactivities, however their structure-activity relationship is still not clear. Herein, a novel low-molecular-weight polysaccharide (LPNP) was isolated and refined from Plumula Nelumbinis. The structure of LPNP was characterized using High-performance gel permeation chromatography (HPGPC), monosaccharide composition analysis, NMR spectroscopy, and methylation analysis. The results revealed that LPNP had a molecular weight of 11.6 kDa, consisting six monosaccharides. Glycosidic linkages →3)-β-L-Araf-(1→, →5)-β-L-Araf-(1→, T-β-L-Araf-(1→, →3)-β-D-Galp-(1→, →4)-α-D-Glcp-(1→, →4)-α-D-Xylf-(1→, T-α-D-Xylp-(1→, and T-α-D-Glcp-(1→ were the main types of linkages in LPNP. LPNP could strongly protect RAW264.7 cells from H2O2-induced damage by preserving stable cell viability, reducing reactive oxygen species (ROS) and malondialdehyde (MDA) production and lactate dehydrogenase (LDH) secretion, enhancing catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity, and increasing glutathione (GSH) content. LPNP inhibited the activation of the MAPK/NF-κB cell pathway, thereby decreasing the expression of NO, INF-γ, TNF-α, IL-6, and IL-1β. LPNP could be exploited as a prospective source of natural substances in functional foods or pharmaceuticals.

In-Source Decay MALDI and High-Energy Collision-Induced Dissociation Mass Spectrometry of Alkali Metal-Adducted Underivatized Oligosaccharides.

In-source decay (ISD) and high-energy collision-induced dissociation (HE-CID) were explored to provide structural information on alkali metal-adducted linear and stacked oligosaccharides (oligosaccharides with increased flexibility due to linkage type). These oligosaccharides include isomeric tetrasaccharides, maltoheptaose, and several human milk oligosaccharides (HMOs). Matrix-assisted laser desorption ionization (MALDI) ion production efficiency, as well as the product ion intensities, and the number of product ions formed in ISD and HE-CID of these oligosaccharides were influenced by the matrix, the ionic radius of the metal ion used for adduction, and the affinity of metal ions for specific functional groups in the oligosaccharides. 2,4,6-Trihydroxyacetophenone (THAP) was the best matrix for HE-CID of oligosaccharides, 4-dimethylaminobenzaldehyde (DMABA) worked best for ISD of tetrasaccharides and pentasaccharides, while 2,5-dihydroxybenzoic acid (DHB) was the best matrix for ISD and HE-CID of long chain oligosaccharides. In general, the number of product ions formed followed the trend Li+ > Na+ > K+ > Rb+ > Cs+, except for HMOs where Na+ ≥ Li+ > K+ > Rb+ > Cs+ occurred. The type of product ions formed and their intensities varied based on the position of the glycosidic bond linkage and the content of the monosaccharide. ISD and HE-CID produced diagnostic ions that could structurally differentiate isomers. Overall, HE-CID of alkali-metal adducted oligosaccharides produces intense glycosidic bond cleavages and low intensity cross-ring and internal cleavages. In contrast, ISD generates mainly cross-ring cleavages and internal cleavages at intensities higher than in HE-CID. In addition, ISD produced unique product ions that complement results from HE-CID.

Isolation and characterization of a nephroprotective polysaccharide from Dendrobium chrysotoxum Lindl against LPS-induced acute kidney injury mice

The structure and bioactivity of a novel polysaccharide from Dendrobium Chrysotoxum Lindl (DCP-1) were investigated. The crude polysaccharides of Dendrobium Chrysotoxum Lindl (DCP) were extracted by hot water extraction, and the protein was removed by enzymatic hydrolysis and Sevage. After purification, the chemical structure of polysaccharides was identified by infrared spectroscopy, methylation analysis and nuclear magnetic resonance spectroscopy. Then, a mouse model of acute kidney injury (AKI) was constructed using lipopolysaccharide (LPS), and pretreated with DCP. Structure characterization demonstrated that the number-average molecular weight and mass average molar mass of DCP-1 were 28.43 kDa and 15.00 kDa, respectively. DCP-1 mainly consisted of mannose (37.8 %) and glucose (55.6 %). The main linkage types of DCP-1 were contained 1,4-Linked Manp and 1,4-Linked Glcp. And DCP-1 was demonstrated to be an O-acetylglucomannan with β-ᴅ-configuration in pyranoid form. Besides, the bioactivity of DCP was further investigated. The results showed that DCP exhibited notable anti-inflammatory activity in LPS-induced AKI mice. After treated with DCP, the creatinine (CREA) and urea nitrogen (BUN) in serum were successfully down-regulated in AKI mice. DCP treatment prevented the characteristic morphological changes of LPS-induced renal tubular injury. The results showed that DCP treatment significantly reduced the concentration of oxidative damage indicators (MDA, SOD) and the expression of inflammatory indices (TNF-α, IL-6, MCP-1, COX-2). In general, the newly extracted polysaccharide DCP showed excellent nephroprotective effect, which enabled it to be an ideal natural medicine for kidney diseases therapy.

Halogen Bonding Involving Isomeric Isocyanide/Nitrile Groups.

2,3,5,6-Tetramethyl-1,4-diisocyanobenzene (1), 1,4-diisocyanobenzene (2), and 1,4-dicyanobenzene (3) were co-crystallized with 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) to give three cocrystals, 1·1,3,5-FIB, 2·2(1,3,5-FIB), and 3·2(1,3,5-FIB), which were studied by X-ray diffraction. A common feature of the three structures is the presence of I···Cisocyanide or I···Nnitrile halogen bonds (HaBs), which occurs between an iodine σ-hole and the isocyanide C-(or the nitrile N-) atom. The diisocyanide and dinitrile cocrystals 2·2(1,3,5-FIB) and 3·2(1,3,5-FIB) are isostructural, thus providing a basis for accurate comparison of the two types of noncovalent linkages of C≡N/N≡C groups in the composition of structurally similar entities and in one crystal environment. The bonding situation was studied by a set of theoretical methods. Diisocyanides are more nucleophilic than the dinitrile and they exhibit stronger binding to 1,3,5-FIB. In all structures, the HaBs are mostly determined by the electrostatic interactions, but the dispersion and induction components also provide a noticeable contribution and make the HaBs attractive. Charge transfer has a small contribution (<5%) to the HaB and it is higher for the diisocyanide than for the dinitrile systems. At the same time, diisocyanide and dinitrile structures exhibit typical electron-donor and π-acceptor properties in relation to the HaB donor.

Biochemical characterization of glycoside hydrolase family 31 α-glucosidases from Myceliophthora thermophila for α-glucooligosaccharide synthesis

The transglucosidase activity of GH31 α-glucosidases is employed to catalyze the synthesis of prebiotic isomaltooligosaccharides (IMOs) using the malt syrup prepared from starch as substrate. Continuous mining for new GH31 α-glucosidases with high stability and efficient transglucosidase activity is critical for enhancing the supply and quality of IMO preparations. In the present study, two α-glucosidases (MT31α1 and MT31α2) from Myceliophthora thermophila were explored for biochemical characterization. The optimum pH and temperature of MT31α1 and MT31α2 were determined to be pH 4.5 and 65 °C, and pH 6.5 and 60 °C, respectively. Both MT31α1 and MT31α2 were shown to be stable in the pH range of 3.0 to 10.0. MT31α1 displayed a high thermostability, retaining 60 % of activity after incubation for 24 h at 55 °C. MT31α1 is highly active on substrates with all types of α-glucosidic linkages. In contrast, MT31α2 showed preference for substrates with α-(1→3) and α-(1→4) linkages. Importantly, MT31α1 was able to synthesize IMOs and the conversion rate of maltose into the main functional IMOs components reached over 40 %. Moreover, MT31α2 synthesizes glucooligosaccharides with (consecutive) α-(1→3) linkages. Taken together, MT31α1 and MT31α2, showing distinct substrate and product specificity, hold clear potential for the synthesis of prebiotic glucooligosaccharides.

Dioxin-Linked Covalent Organic Framework-Supported Palladium Complex for Rapid Room-Temperature Suzuki–Miyaura Coupling Reaction

Covalent organic framework (COF)-supported palladium catalysts have garnered enormous attention for cross-coupling reactions. However, the limited linkage types in COF hosts and their suboptimal catalytic performance have hindered their widespread implementation. Herein, we present the first study immobilizing palladium acetate onto a dioxin-linked COF (Pd/COF-318) through a facile solution impregnation approach. By virtue of its permanent porosity, accessible Pd sites arranged in periodic skeletons, and framework robustness, the resultant Pd/COF-318 exhibits exceptionally high activity and broad substrate scope for the Suzuki–Miyaura coupling reaction between aryl bromides and arylboronic acids at room temperature within an hour, rendering it among the most effective Pd/COF catalysts for Suzuki–Miyaura coupling reactions to date. Moreover, Pd/COF-318 demonstrates excellent recyclability, retaining high activity over five cycles without significant deactivation. The leaching test confirms the heterogeneity of the catalyst. This work uncovers the vast potential of dioxin-linked COFs as catalyst supports for highly active, selective, and durable organometallic catalysis.

Tailoring the surface chemistry of lignin nanoparticles using fungal laccases: Insights on the oxidation mechanisms

The functionalization of lignin nanoparticles (LNPs) can increase the application of such systems by grafting different ligands and tailoring the surface chemistry. However, these modifications are conventionally performed using harsh and energy-demanding methods. Laccase-induced reactions represent a green synthetic approach to modify the lignin, either to depolymerize or induce crosslinking of lignin monomeric units, usually assisted by redox mediators. In this study, we aim to characterize the oxidation mechanism and its effect on the surface chemistry and polymerization of LNPs that exhibit different proportions of structural units and S/G ratios in their composition, using five fungal laccases produced in house and two commercial laccases, without the presence of mediators. Our results suggest that the in house produced laccases induce about a 5-fold increase in the particle size and absorbance values of the LNPs with low S/G ratio, compared to the untreated LNPs, indicating the formation of dimeric product through CC type of linkages and consequent polymerization and crosslinking of these LNPs. Contrarily, LNPs presenting high S/G ratio show a decrease in the phenolic content along with an increase in the percentage of oxidized syringyl-type units after laccase treatment, suggesting a preferred Cα–OH type of oxidation. Overall, this study provides new insights on the mechanism of laccase-assisted oxidation and polymerization of LNPs presenting different monomeric composition, which can greatly increase the application of further tailored LNPs in different sectors, including biomedical and food sciences.

Mapping Stakeholders and Their Networks for Strategic Communication in the Romanian Health Sector – A Public Relations Approach

Abstract Introduction: Communication has a significant role in achieving objectives in the medical sector. It involves information, collaboration, partnership and starts from understanding the profile, needs and interests of main stakeholders and their relationship networks. Healthcare public relations (HPR) provides a useful framework for strategic communication, by identifying stakeholders and their potential connections, designing, and implementing interactions that lead to positive results for all those involved and for supporting health in general. The current study proposes a mapping of stakeholders and networks in the healthcare system in Romania, as premises for efficient HPR. Public relations and stakeholder approach: Professional public relations (PR) is based on two-way communication, implying partnership and collaboration. Stakeholder theory, as approached within PR framework, is appropriate for present realities, considering the network society and the interdependency between actors. Methodology: This is an exploratory study using in-depth documentation and analysis of public data (statistics, reports, legislation), accessible online. Results: The author provides a graphic and verbal map of stakeholders in the Romanian health sector (patients, medical body, pharmacists, health facilities, academia, healthcare producers and suppliers, authorities and international bodies, professional representatives, NGOs, and mass media), and their networks. Five types of linkages are highlighted, by considering the criteria of the impact the connection has on healthcare (direct and indirect) and the connection grounds (functional, support), and including mixed interactions. Discussion: Results and implications of the analysis are discussed in relation to previous scholarship. The HPR approach is emphasized as an advantageous framework for strategic communication in the healthcare sector. Conclusions: Healthcare communication implies a complex process of documentation, planning, strategy, and implementation. Its outcomes are translated into more than plain public information or promotion of specific products and services in this area. By focusing on interconnectivity, and mutual understanding, HPR fosters common engagement and collaboration between stakeholders, within their natural networks, and offers valuable strategic communication coordinates for the medical sector and its challenges.