MALDI-TOF Analysis Research Articles

Effects of altered N-glycan structures of Cryptococcus neoformans mannoproteins, MP98 (Cda2) and MP84 (Cda3), on interaction with host cells

Cryptococcus neoformans is an opportunistic human fungal pathogen causing lethal meningoencephalitis. It has several cell wall mannoproteins (MPs) identified as immunoreactive antigens. To investigate the structure and function of N-glycans assembled on cryptococcal cell wall MPs in host cell interactions, we purified MP98 (Cda2) and MP84 (Cda3) expressed in wild-type (WT) and N-glycosylation-defective alg3 mutant (alg3Δ) strains. HPLC and MALDI-TOF analysis of the MP proteins from the WT revealed protein-specific glycan structures with different extents of hypermannosylation and xylose/xylose phosphate addition. In alg3Δ, MP98 and MP84 had truncated core N-glycans, containing mostly five and seven mannoses (M5 and M7 forms), respectively. In vitro adhesion and uptake assays indicated that the altered core N-glycans did not affect adhesion affinities to host cells although the capacity to induce the immune response of bone-marrow derived dendritic cells (BMDCs) decreased. Intriguingly, the removal of all N-glycosylation sites on MP84 increased adhesion to host cells and enhanced the induction of cytokine secretion from BMDCs compared with that on MP84 carrying WT N-glycans. Therefore, the structure-dependent effects of N-glycans suggested their complex roles in modulating the interaction of MPs with host cells to avoid nonspecific adherence to host cells and host immune response hyperactivation.

Circular Dichroism Study of Orexin B under Oxidative Stress Conditions.

The neuropeptides orexin A and B regulate various vital functions of the body, such as sleep/wake states, metabolism, and energy homeostasis. A loss of their physiological activity, with reduced ability to recognize their receptors, is suspected to be associated with oxidative stress conditions. These are related to excessive presence of reactive oxygen and nitrogen species, as well as of reactive lipoxidation byproducts. With the aim of evaluating the effects of oxidative stress on the secondary structure of orexin peptides, orexin B was synthesized and characterized by circular dichroism spectroscopy under different conditions. In aqueous solution it presents an unordered conformation, while in a membrane mimetic environment it assumes a helical structure. The effects of oxidative stress were evaluated exposing it to both oxygen and nitrogen radicals as well as to lipoxidation byproducts. The results showed that ROS, but not NRS, induced appreciable conformational changes, and only in the membrane mimetic environment. Lipoxidation byproducts, instead, led to secondary structure modifications much more evident than those induced by the direct action of ROS and RNS, and in both analyzed media. Additionally, MALDI-TOF analyses detected mass variations in the peptide attributable to oxidation of the C-terminal Met residue and deamination of asparagine in the Asn-His sequence. Taken together, all these data seem to confirm the involvement of oxidative processes in dysfunctions of the orexinergic system.

Partial characterization of purified glycoprotein from nutshell of Arachis hypogea L. towards macrophage activation and leishmaniacidal activity.

Arachis hypogea L. protein fraction-2 (AHP-F2) from the Peanut shell was extracted and characterized and its potent immunomodulatory and anti-leishmanial role was determined in this present study. AHP-F2 was found to be a glycoprotein as the presence of carbohydrates were confirmed by the analysis of high-performance liquid chromatography (HPLC) yielded glucose, galactose, mannose, and xylose. AHP-F2 molecular mass was found to be ∼28kDa as indicated in MALDI-TOF and peptide mass fingerprinting analysis followed by Mascot search. The peptide matches revealed the similarity of the mannose/glucose binding lectin with 71.07% in the BLAST analysis. After that, the 3D structure of the AHP-F2 model was designed and validated by the Ramachandran plot. The immunomodulatory role of AHP-F2 was established in murine peritoneal macrophages as induction of nitric oxide (NO), and stimulation of proinflammatory cytokines (IL-12 and IFN-γ) in a dose-dependent manner was observed. Interestingly, it was also found that AHP-F2 has interacted with the innate immune receptor, toll-like receptors (TLRs) as established in molecular docking as well as mRNA expression. The anti-leishmanial potential of AHP-F2 was revealed with a prominent inhibition of amastigote growth within the murine macrophages with prompt induction of nitrite release. Altogether, the isolated AHP-F2 from Arachis hypogea L. has strong immunomodulatory and anti-leishmanial potential which may disclose a new path to treat leishmaniasis.

Assessment of antiproliferative and toxic effects of a peptide from Momordica dioica using in vitro and in vivo studies

Abstract: Inflammation occurs during a cascade reaction to cause damage to the tissues. Increased oxidant and cytokine expression were observed in the damaged tissues. Inflammatory bowel disease (IBD) may be a chronic and lethal disease of inflammation in gastro enteric tissue characterized by intestinal inflammation. The objective of the study was to investigate the toxicological effects of Peptide extract from Momordica dioica in treating colitis conditions. The isolated protein was digested with trypsin enzyme with an E:S ratio of 1:100 and the hydrolyzed peptides were analyzed using LCMS. The peak obtained at 678.67 Da at 17mins showed hydrophobic peptide and MALDI-TOF analysis which showed similar peaks at 3388.7Da. The results from the MTT assay showed the IC50 value of the peptide extract at 100µg/ml. Similarly, the acridine orange staining showed decreased green fluorescent nuclei cells than red fluorescent acidic vesicular organelles indicating autophagy-dependent cell death. The peptide extract displayed a cell viability effect on Colo-205 cells at 100 μg/ml when compared to the control. In the acute toxicity test, the mice were orally receiving peptide extract at a dose of 50-250 mg/kg BW for 14 days. The significant adverse effects were evident at a dose of 250mg/kg BW indicating that the LD50 value is lesser than 250 mg/kg.

Antimicrobial resistance and its relationship with antimicrobial use on Austrian dairy farms.

The aim of this study was to investigate the prevalence of ESBL/AmpC-producing E. coli and the resistance pattern of commensal E. coli, as well as the link between the use of antibiotics (AMU) and the occurrence of resistance in E. coli on Austrian dairy farms. AMU data from 51 farms were collected over a one-year period in 2020. Fecal samples were collected from cows, pre-weaned and weaned calves in 2020 and 2022. Samples were then analyzed using non-selective and selective agar plates, E. coli isolates were confirmed by MALDI-TOF analysis. Broth microdilution was used for antimicrobial susceptibility testing. The AMU of each farm was quantified as the number of Defined Daily Doses (nDDDvet) and Defined Course Doses (nDCDvet) per cow and year. Cephalosporins (mean 1.049; median 0.732 DDDvet/cow/year) and penicillins (mean 0.667; median 0.383 DDDvet/cow/year) were the most frequently used antibiotics on these farms, followed by tetracyclines (mean 0.275; median 0.084 DDDvet/cow/year). In 2020, 26.8% of the E. coli isolated were resistant to at least one antibiotic class and 17.7% of the isolates were classified as multidrug resistant (≥3 antibiotic classes). Out of 198 E. coli isolates, 7.6% were identified as extended-spectrum/AmpC beta-lactamase (ESBL/AmpC) producing E. coli. In 2022, 33.7% of E. coli isolates showed resistance to at least one antibiotic and 20.0% of isolates displayed multidrug resistance. Furthermore, 29.5% of the samples carried ESBL/AmpC-producing E. coli. In 2020 and 2022, the most frequently determined antibiotic resistances among commensal E. coli isolates were to tetracyclines, sulfonamides and penicillins. In addition, pre-weaned calves had the highest resistance rates in both years. Statistical analyses showed a significant association between low and high use AMU classifications for penicillins (in nDDDvet/cow/year) and their respective resistance among commensal E. coli isolates in 2020 (p = 0.044), as well as for sulfonamide/trimethoprim (p = 0.010) and tetracyclines (p = 0.042). A trend was also noted between the total amount of antibiotics used on farm in 2020 (by nDDDvet/cow/year) and multidrug resistances in commensal E. coli isolated on farm that year (p = 0.067). In conclusion, the relationship between AMU and antimicrobial resistance (AMR) on dairy farms continues to be complex and difficult to quantify.

Reaction-based energy level modulation of a cyclometalated iridium complex for electrochemiluminescent detection of formaldehyde.

Formaldehyde is a toxic compound present in both the environment and living systems, and its detection is important due to its association with various pathological process. In this study, we report a new electrochemiluminescence (ECL) probe based on a cyclometalated iridium complex (IrHAA) for the selective detection of formaldehyde. The homoallylamine moiety in IrHAA reacts with formaldehyde, undergoing a 2-aza-Cope-rearrangement reaction to form a formyl group. Significant changes in the electronic properties and molecular orbital energies of the iridium complex through the functional group transformation result in enhanced ECL and radiometric phosphorescence changes, enabling the quantitative and selective detection of formaldehyde. The energetic requirements for ECL sensing were investigated, highlighting the importance of the excited state energy for achieving efficient ECL. The sensing mechanism was elucidated using NMR spectroscopy and MALDI-TOF analysis.

Secretome Analysis of Human Nasal Fibroblast Identifies Proteins That Promote Wound Healing.

Conditioned medium from cultured fibroblast cells is recognized to promote wound healing and growth through the secretion of enzymes, extracellular matrix proteins, and various growth factors and cytokines. The objective of this study was to profile the secreted proteins present in nasal fibroblast conditioned medium (NFCM). Nasal fibroblasts isolated from human nasal turbinates were cultured for 72h in Defined Keratinocytes Serum Free Medium (DKSFM) or serum-free F12: Dulbecco's Modified Eagle's Medium (DMEM) to collect conditioned medium, denoted as NFCM_DKSFM and NFCM_FD, respectively. SDS-PAGE was performed to detect the presence of protein bands, followed by MALDI-TOF and mass spectrometry analysis. SignalP, SecretomeP, and TMHMM were used to identify the secreted proteins in conditioned media. PANTHER Classification System was performed to categorize the protein according to protein class, whereas STRING 10 was carried out to evaluate the predicted proteins interactions. SDS-PAGE results showed the presence of various protein with molecular weight ranging from ~10kDa to ~260kDa. Four protein bands were identified using MALDI-TOF. The analyses identified 104, 83, and 7 secreted proteins in NFCM_FD, NFCM_DKSFM, and DKSFM, respectively. Four protein classes involved in wound healing were identified, namely calcium-binding proteins, cell adhesion molecules, extracellular matrix proteins, and signaling molecules. STRING10 protein prediction successfully identified various pathways regulated by secretory proteins in NFCM. In conclusion, this study successfully profiled the secreted proteins of nasal fibroblasts and these proteins are predicted to play important roles in RECs wound healing through various pathways.

MUF Resins Improved by Citric Acid as Adhesives for Wood Veneer Panels

This article presents the first applied results of using citric acid in combinations with a melamine-urea-formaldehyde (MUF) resin for bonding wood veneers. The chemical reactions involved are shown based on a MALDI ToF analysis of the reaction of the MUF resin with citric acid. The preliminary results of the physical and mechanical properties of the LVL prepared are also presented. Veneers from Populus sp were used to manufacture 5-layer laminated veneer lumber (LVL) of small dimensions. Five combinations of the amount of citric acid, MUF spread rate and pressing parameters were tested. LVL bonded with 20% of citric acid + 100 g/m2 of MUF, hot-pressed using a 3-step process with maximum 1.5 MPa of pressure yielded the board with better dimensional stability and mechanical properties. It could be concluded that citric acid in combination with MUF can be used for bonding wood veneer and the research should be continued to study further the parameters involved and to enhance the results.

Application of MALDI-TOF Mass Spectrometry for Non-invasive Diagnostics of Mucopolysaccharidosis IIIA

Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disorder (LSD) caused by deficiency of lysosomal N-sulphoglucosamine sulphohydrolase, which is one of four enzymes involved in heparan sulfate degradation. Traditional methods used for MPS IIIA diagnostics usually constitute of selective screening, based on the analysis of urinary glycosaminoglycans, further enzymatic assays in leukocytes, and mutation analysis. Nowadays, some LSDs, including mucopolysaccharidoses, can be precisely diagnosed by mass spectrometry-based techniques. Up to this date, there are no comprehensive studies of MPS IIIA diagnostics by MALDI-TOF analysis of free oligosaccharides in urine published. In the presented work, MALDI-TOF/TOF analysis of permethylated oligosaccharides was performed to obtain the set of glyco-biomarkers that together form the specific fingerprint of this disease. Early and accurate diagnostics of MPS IIIA is crucial to stabilize the progressive cellular damage and improve the overall well-being of patients.

Purification and characterization of platelet aggregation inhibitor from the venom of Bitis arietans

Disintegrins are the antagonists of integrin receptors that can be found mostly in snakes’ venom. They can inhibit platelet aggregation, thus preventing the formation of blood clots. By blocking the integrin receptors of cancer cells, disintegrins can inhibit proliferation and metastasis. Thus, the search for new sources of disintegrins and development of methods of their purification is an important task of modern biotechnolo­gy. This work was dedicated to the purification and characterization of inhibiting polypeptides from Bitis arietans­ venom. Crude venom of B. arietans was fractionated using ion-exchange chromatography on Q Sepharose followed by size-exclusion chromatography on Superdex 75 using FPLC method. Analysis of molecular weight of protein components was performed using SDS-PAGE and MALDI-TOF analysis on Voyager-DE. Aggregation of platelet-rich plasma (PRP) in the presence of platelet aggregation inhibitor was investigated using aggregometry on the AR2110. MTT test was used for measuring HeLa cells proliferation and survival in vitro. Two-step chromatography allowed us to obtain fraction that contained polypeptides possessing the dose-dependent inhibitory action on adenosine diphosphate (ADP)-induced platelet aggregation in PRP. SDS-PAGE showed that obtained fraction contained two polypeptides with molecular weight 9.0 and 13.67 kDa according­ to MALDI-TOF analysis. Purified polypeptides inhibited ADP-induced platelet aggregation with IC50 0.09 mg/ml. However, 0.005 mg/ml of fraction suppressed viability of HeLa cells according to MTT test on 20%. Discovered biological effects of fractions allowed us to conclude the possible use of these polypeptides as anti-aggregatory or anti-proliferative agents. Keywords: antithrombotic action, disintegrins, glycoprotein IIb/IIIa, platelets, snake venom

Incidental finding of Clostridium perfringens on human corpses used for the anatomy course

Post-mortem specimens used for anatomy teaching are commonly embalmed using compositions of chemicals, with the objective to maintain tissue quality and to avoid putrefaction. Monitoring for bacterial or fungal contamination is becoming increasingly important especially when measures are taken to minimize exposure by chemicals such as formaldehyde. In this case, random swabs were taken from six corpses embalmed with ethanol-glycerin and Thiel embalming. Cultures and MALDI-TOF analyses yielded four cases of Clostridium perfringens contamination. C. perfringens is of special interest as a human pathogen. A potential source was identified in the containers filled with the moistening solution. Cross contamination with Clostridium species has likely occurred between corpses sharing the moistening solution and soaking the cover linen directly within the containers. To minimize any risk for those exposed, the moistening solutions were discarded and all equipment thoroughly disinfected. The specimens had to be cremated as they formed a potential source of Clostridium spores. Deviating from previous routines it was formalized that the cover linen must not be submerged in the moistening contains rather than moistening the specimens directly with dedicated vessels. Follow-up analyses yielded no further contamination with C. perfringens.

Functional Characterization, Mechanism, and Mode of Action of Putative Streptomycin Adenylyltransferase from Serratia marcescens.

Nosocomial infections are serious threats to the entire world in healthcare settings. The major causative agents of nosocomial infections are bacterial pathogens, among which Enterobacteriaceae family member Serratia marcescens plays a crucial role. It is a gram-negative opportunistic pathogen, predominantly affecting patients in intensive-care units. The presence of intrinsic genes in S. marcescens led to the development of resistance to antibiotics for survival. Complete scanning of the proteome, including hypothetical and partially annotated proteins, paves the way for a better understanding of potential drug targets. The targeted protein expressed in E. coli BL21 (DE3) pLysS cells has shown complete resistance to aminoglycoside antibiotic streptomycin (>256 MCG). The recombinant protein was purified using affinity and size-exclusion chromatography and characterized using SDS-PAGE, western blotting, and MALDI-TOF analysis. Free phosphate bound to malachite green was detected at 620 nm, evident of the conversion of adenosine triphosphate to adenosine monophosphate during the adenylation process. Similarly, in the chromatographic assay, adenylated streptomycin absorbed at 260 nm in AKTA (FPLC), confirming the enzyme-catalyzed adenylation of streptomycin. Further, the adenylated product of streptomycin was confirmed through HPLC and mass spectrometry analysis. In conclusion, our characterization studies identified the partially annotated hypothetical protein as streptomycin adenylyltransferase.

Spontaneous alternating copolymerization of aziridines with tosyl isocyanate toward polyureas

We report a new synthetic approach toward cyclic polyureas through alternating copolymerization of aziridines with tosyl isocyanate. Aziridines (ethyleneimine, and (S)-2-benzylaziridine) react with tosyl isocyanate spontaneously in the absence of any catalyst to produce polyureas. The obtained polyureas exhibit an alternating structure as determined by NMR and MALDI-TOF MS analysis. MALDI-TOF analysis indicates that the synthesized polyureas are cyclic. A spontaneous zwitterionic copolymerization mechanism is proposed. DFT calculations reveal that the copolymerization of tosyl isocyanate with ethyleneimine is more kinetically and thermodynamically favored than 2-benzylaziridine.

Development of Water Repellent, Non-Friable Tannin-Furanic-Fatty Acids Biofoams.

Tannin-furanic foams were prepared with a good yield using the addition of relatively small proportions of a polyflavonoid tannin extract esterified with either palmitic acid, oleic acid, or lauric acid by its reaction with palmitoyl chloride, oleyl chloride, or lauryl chloride. FTIR analysis allowed us to ascertain the esterification of the tannin, and MALDI-TOF analysis allowed us to identify a number of multi-esterified flavonoid oligomers as well as some linked to residual carbohydrates related to the equally esterified tannin. These foams presented a markedly decreased surface friability or no friability at all, and at densities lower than the standard foam they were compared to. Equally, these experimental foams presented a much-improved water repellence, as indicated by their initial wetting angle, its small variation over time, and its stabilization at a high wetting angle value, while the wetting angle of the standard foam control went to zero very rapidly. This conclusion was supported by the calculation of the total surface energy of their surfaces as well as of their dispersive and polar components.

Characterization of a potent plant growth promoting fungal strain Aspergillus fumigatus MCC 1721 with special reference to indole-3-acetic acid production

In the present study, indole-3-acetic acid (IAA) producing plant growth promoting fungus was isolated from rice field of Purba Bardhaman district, West Bengal, India. Among the isolated 6 strains, AP2 (Aspergillus fumigatus) was selected as best-performing plant growth promoting fungal strain as it was an efficient indole-3-acetic acid producer as well as exhibits different plant growth promoting ability viz, phosphate solubilization, siderophore production, ammonia and hydrogen cyanide production etc. Media and different growth conditions (pH, temperature, concentration of sodium chloride) were optimized for augmentation of the indole-3-acetic acid production. The genus of the selected isolate AP2 was identified as Aspergillus fumigatus both by 18S rDNA sequence-based homology and MALDI-TOF analyses of ribosomal protein. Plant growth promoting ability of Aspergillus fumigatus has been confirmed by measuring different morphological and biochemical growth parameters in Trigonella foenum-graecum L. So, AP2 (Aspergillus fumigatus) can be considered as novel plant growth promoting fungal strain that can be applied as bio-inoculants on agricultural field.

Influence of Oxidation and Dialysis of Phlorotannins on Bioactivity and Composition of Ultrasound-Assisted Extracts from Ascophyllum nodosum.

The isolation and chemical characterization of phlorotannins has gained special attention in recent years due to their specific health-promoting benefits. Flow-cell ultrasound-assisted extraction (90 W/cm2 of sonication power, 2 min of retention time and 20 g solvent/g algae of liquid-solid ratio) was carried out by using double-distilled water (WE) and acetone:water mixture (AWE) as extraction solvents. The AWE showed a higher total polyphenols content (TPC), carbohydrates (CHOs) and antioxidant activities than WE. However, when the WE was purified by using Amberlite XAD16 column, the purified WE (PWE) showed similar a TPC, decreased CHOs and increased antioxidant activity compared to WE. The oxidation of the PWE extract was evaluated under natural, forced and severe oxidation condition for 120 h. Only severe oxidation conditions were able to significantly reduce TPC and antioxidant activities. PWE was dialyzed (20, 10, 3.5 and 2 kDa). The main bioactive fraction of phlorotannins was obtained from 10 to 20 kDa. CHOs were distributed in fractions below 20 kDa. MALDI-TOF analysis was performed for PWE, PD20 and PD2 extracts to analyze the degree of polymerization of phlorotannins, which ranged from 4 to 17 phloroglucinol units/molecule. Fragmentation patterns allowed the proximate identification of several phlorotannins in Ascophyllum nodosum extracts.

Phenyl boronic acid -PEG-stearic acid biomaterial-based and sialic acid targeted nanomicelles for colon cancer treatment

This study aims to develop and evaluate a sialic acid receptor-targeting biomaterial for an effective delivery of usnic acid (UA). The novel biomaterial system is composed of three different parts; (1) stearic acid (SA) a hydrophobic core for encapsulation of UA, (2) PEG spacer to make conjugate amphiphilic, and (3) at the periphery phenylboronic acid (PBA) for cancer cell targeting. The synthesized PBA-PEG-SA biomaterial was characterized by FTIR NMR, and MALDI-TOF analysis. An average molecular weight of PBA-PEG-SA was about 3896 Da. The PBA-PEG-SA biomaterial was self-assembled into the nanomicelles with a 460 μg/mL CMC value. The UA-loaded PBA-PEG-SA nanomicelles (UPNM) were analysed by DLS, TEM, FTIR NMR, DSC and XRD techniques. The average particle size of UPNM was about 160 nm and its spherical nature was confirmed by TEM analysis. The synthesized biomaterial provided a pH-sensitive and controlled release of encapsulated UA with < 10% release at gastric pH 1.2 while > 90% release at intestinal pH 6.8. In vitro cytotoxicity potential of developed UPNM was investigated against HCT116 human colon cancer cells. The in vitro results proved that the synthesized PBA-PEG-SA biomaterial had good biocompatibility and PBA decorated nanomicelles could be successfully uptaken by HCT116 cancer cells. The observed IC50 value for UPNM (5.37 ± 0.78 μg/mL) was significantly lower (p < 0.01) than pure UA (8.57 ± 0.26 μg/mL) or non-targeted UA-loaded nanomicelles (8.36 ± 0.63 μg/mL). Further, the targeted nanomicelles showed higher apoptosis and greater control over the colony formation ability of HCT116 cells than pure drug or non-targeted UA-loaded nanomicelles.

Phosphazene-Containing Epoxy Resins Based on Bisphenol F with Enhanced Heat Resistance and Mechanical Properties: Synthesis and Properties.

Organophosphazenes are of interest due to the combination of increased mechanical and thermal properties of polymer materials obtained with their use, however, they are characterized by a complex multi-stage synthesis. Moreover, the high viscosity of phosphazene-containing epoxy resins (PhER) makes their processing difficult. To simplify the synthesis of PhER, a one-step method was developed, and bisphenol F was chosen, which also provided a decrease in viscosity. In the current study, PhER were formed by a one-stage interaction of hexachlorocyclotriphosphazene (HCP) with bisphenol F isomers and epichlorohydrin in the presence of alkali, which was a mixture of epoxycyclophosphazenes (ECPh) with a functionality from 1 to 4 according to the results of MALDI-TOF analysis. Conventional epoxy resins based on bisphenol F, also formed during the process, showed high mechanical properties and glass transition temperature, and the reactivity of the obtained resins is similar to the base epoxy resins based on bisphenols A and F. Cured PhER had higher or the same mechanical properties compared to base epoxy resins based on bisphenol A and F, and a glass transition temperature comparable to base epoxy resins based on bisphenol F: glass transition temperature (Tg) up to 174.5 °C, tensile strength up to 74.5 MPa, tensile modulus up to 2050 MPa, tensile elongation at break up to 6.22%, flexural strength up to 146.6 MPa, flexural modulus up to 3630 MPa, flexural elongation at break up to 9.15%, and Izod impact strength up to 4.01 kJ/m2. Analysis of the composition of the obtained PhER was carried out by 1H and 31P NMR spectroscopy, MALDI-TOF mass spectrometry, X-ray fluorescence elemental analysis, and contained up to 3.9% phosphorus and from 1.3% to 4.2% chlorine. The temperature profile of the viscosity of the resulting epoxy resins was determined, and the viscosity at 25 °C ranged from 20,000 to 450,000 Pa·s, depending on the ratio of reagents. The resins studied in this work can be cured with conventional curing agents and, with a low content of the phosphazene fraction, can act as modifiers for traditional epoxy resins, being compatible with them, to increase impact strength and elasticity while maintaining the rest of the main mechanical and processing properties, and can be used as a resin component for composite materials, adhesives, and paints.

Sequence-Reversible Construction of Oxygen-Rich Block Copolymers from Epoxide Mixtures by Organoboron Catalysts.

Switchable catalysis, in combination with epoxide-involved ring-opening (co)polymerization, is a powerful technique that can be used to synthesize various oxygen-rich block copolymers. Despite intense research in this field, the sequence-controlled polymerization from epoxide congeners has never been realized due to their similar ring-strain which exerts a decisive influence on the reaction process. Recently, quaternary ammonium (or phosphonium)-containing bifunctional organoboron catalysts have been developed by our group, showing high efficiency for various epoxide conversions. Herein, we, for the first time, report an operationally simple pathway to access well-defined polyether-block-polycarbonate copolymers from mixtures of epoxides by switchable catalysis, which was enabled through thermodynamically and kinetically preferential ring-opening of terminal epoxides or internal epoxides under different atmospheres (CO2 or N2) using one representative bifunctional organoboron catalyst. This strategy shows a broad substrate scope as it is suitable for various combinations of terminal epoxides and internal epoxides, delivering corresponding well-defined block copolymers. NMR, MALDI-TOF, and gel permeation chromatography analyses confirmed the successful construction of polyether-block-polycarbonate copolymers. Kinetic studies and density functional theory calculations elucidate the reversible selectivity between different epoxides in the presence/absence of CO2. Moreover, by replacing comonomer CO2 with cyclic anhydride, the well-defined polyether-block-polyester copolymers can also be synthesized. This work provides a rare example of sequence-controlled polymerization from epoxide mixtures, broadening the arsenal of switchable catalysis that can produce oxygen-rich polymers in a controlled manner.

Isolation and Some Basic Characteristics of Lactic Acid Bacteria from Honeybee (Apis mellifera L.) Environment—A Preliminary Study

In light of the phenomenon of colony collapse disorder, there has been a growing interest in finding natural and ecological ways for improving honeybee health. The aim of this scientific research was the isolation and characterization of LAB, which in the future could show the potential to construct a protective preparation for honeybees. After performing MALDI-TOF analysis, of a total of 76 bacterial strains isolated from flowers and honeybee products, 31 were identified as Pediococcus pentosaceus, 26 as Pediococcus acidilactici, and 19 as Lactiplantibacillus plantarum. The characterization of the isolated LAB displayed that CO2 production was present in 52 strains. The highest biomass productivity was observed in the case of strain 9/1 isolated from red clover (Trifolium pratense L.) with biomass productivity equal to 2.100. All isolated bacterial strains showed the ability to produce lactic acid. The strain 13/3 isolated from small-leaved lime (Tilia cordata L.) displayed the highest lactic acid production capacity in 100 mL of culture, i.e., 1.903 g of lactic acid. The carbohydrate assimilation pattern was examined using API 50 CH tests. All isolated strains were able to utilize esculin, D-ribose, D-galactose, D-glucose D-fructose, and D-mannose. It was also noted that the reduction of sugars is a strain-dependent ability and is specific for individual strains.