Carboxylic Residues Research Articles

Purification, Identification, Chelation Mechanism, and Calcium Absorption Activity of a Novel Calcium-Binding Peptide from Peanut (Arachis hypogaea) Protein Hydrolysate.

A novel calcium-binding peptide was purified from peanut protein hydrolysate using gel filtration chromatography and identified using HPLC-MS/MS. Its amino acid sequence was determined as Phe-Pro-Pro-Asp-Val-Ala (FPPDVA, named as FA6) with the calcium-binding capacity of 15.67 ± 0.39 mg/g. Then, the calcium chelating characteristics of FPPDVA were investigated using ultraviolet-visible absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, particle size, and zeta potential. The results showed that FPPDVA interacted with calcium ions, the chelation of calcium ions induced FPPDVA to fold and form a denser structure, the calcium-binding sites may mainly involve oxygen atoms from the carboxyl residues of Asp and Ala, and Phe possessed contact energy and carbonyl residues of Val. Microstructure analysis showed that FPPDVA-calcium chelate exhibited a regularly ordered and tightly aggregated sheets or block structures. Additionally, FPPDVA-calcium chelate had good gastrointestinal digestive stability and thermal stability. The results of everted rat intestinal sac and Caco-2 cell monolayer experiments showed that FPPDVA-calcium chelate could promote calcium absorption and transport through the Cav1.3 and TRPV6 calcium channels. These data suggest that FPPDVA-calcium chelate possesses the potential to be developed and applied as calcium supplement.

Carboxyl-BODIPY based fluorescent biomarkers: Spectral characteristics, photostability and possibilities for practical application

A comparative analysis of the structural and solvation factors on the spectral properties, pH stability, photostability, and lipophilicity of BODIPY luminophores containing carboxylic acid residues in α- and meso-position was carried out. The interaction of these BODIPYs with cells of microscopic fungi (Candida albicans and Fusarium solani) was studied. The compounds were found to be stable across a wide range of pH values and exhibited intense fluorescence (to φ ∼ 94%) at 508–587 nm. The introduction of a carboxylic acid residue into the meso-position of the BODIPY core causes a noticeable increase (almost ∼2 times) of the Stokes shift compared to the meso-unsubstituted analogues. On the other hand, α-carboxyl-BODIPYs showed a red shift in both the absorption and fluorescence bands. Effective fluorescence quenching (up to 40–80%) was observed in electron donor solvents for carboxyl-BODIPYs, especially for the carboxylic acid BODIPY with a thiophene substituent. The presence of a carboxyl group in the α-position of the BODIPY increased its affinity to hydrophilic media by approximately ∼1.2–2 times compared to meso-carboxyl-BODIPYs. Given the lack of cytotoxicity, carboxyl-BODIPYs may be recommended as effective biomarkers for examining the differences between a wide range of pathogens causing mycotic.

Tuning the Type 1 Reduction Potential of Multicopper Oxidases: Uncoupling the Effects of Electrostatics and H-Bonding to Histidine Ligands.

In multicopper oxidases (MCOs), the type 1 (T1) Cu accepts electrons from the substrate and transfers these to the trinuclear Cu cluster (TNC) where O2 is reduced to H2O. The T1 potential in MCOs varies from 340 to 780 mV, a range not explained by the existing literature. This study focused on the ∼350 mV difference in potential of the T1 center in Fet3p and Trametes versicolor laccase (TvL) that have the same 2His1Cys ligand set. A range of spectroscopies performed on the oxidized and reduced T1 sites in these MCOs shows that they have equivalent geometric and electronic structures. However, the two His ligands of the T1 Cu in Fet3p are H-bonded to carboxylate residues, while in TvL they are H-bonded to noncharged groups. Electron spin echo envelope modulation spectroscopy shows that there are significant differences in the second-sphere H-bonding interactions in the two T1 centers. Redox titrations on type 2-depleted derivatives of Fet3p and its D409A and E185A variants reveal that the two carboxylates (D409 and E185) lower the T1 potential by 110 and 255-285 mV, respectively. Density functional theory calculations uncouple the effects of the charge of the carboxylates and their difference in H-bonding interactions with the His ligands on the T1 potential, indicating 90-150 mV for anionic charge and ∼100 mV for a strong H-bond. Finally, this study provides an explanation for the generally low potentials of metallooxidases relative to the wide range of potentials of the organic oxidases in terms of different oxidized states of their TNCs involved in catalytic turnover.

Colorimetric Polymer Sensors for Smart Packaging

AbstractNowadays, consumers can estimate the condition of packaged foods only by checking the expiration date on the label. However, this approach is inefficient when it comes to assessing the actual edibility of fresh products, since the events that accelerate the onset of degradation phenomena, such as a rise in temperature, cannot be continuously assessed. In this context, the detection of a different parameter, such as low concentration of amines, can reveal the onset of degradation processes. Here, a colorimetric photonic multilayer sensor is reported for detecting low amine concentrations suitable for sealed packages. The sensor consists of alternating layers of poly(N‐vinylcarbazole) and polyacrylic acid, and its response is based on the selective interaction between the latter and amines. This interaction causes the polymer layers to swell and introduce disorder into the photon structure, resulting in fading its bright color. Since the reaction of these systems is usually reversible, manipulation or false readings are possible due to inapt sealing of the package. It is shown that the activation of carboxylic acid residues of the sensitive polymer with N‐hydroxysuccinimide produces an irreversible response to amine vapor concentrations as low as 3 parts per billion.

Ynamide Coupling Reagent for the Chemical Cross-Linking of Proteins in Live Cells.

Chemical cross-linking of proteins coupled with mass spectrometry analysis (CXMS) is a powerful method for the study of protein structure and protein-protein interactions (PPIs). However, the chemical probes used in the CXMS are limited to bidentate reactive warheads, and the available zero-length cross-linkers are restricted to 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). To alleviate this issue, an efficient coupling reagent, sulfonyl ynamide, was developed as a new zero-length cross-linker that can connect high-abundance carboxyl residues (D/E) with lysine (K) to form amide bonds in the absence of any catalyst. Significant improvement in the cross-linking efficiency and specificity in comparison with traditional EDC/NHS was achieved with model proteins, which includes inter- and intramolecular conjugations. The cross-linked structures were validated by X-ray crystallography. Importantly, this coupling reagent can be successfully used to capture interacting proteins in the whole proteome and can be a useful reagent for probing potential protein-protein interactions in situ.

A Bright Surprise: Live‐Cell Labeling with Negatively Charged Fluorescent Probes based on Disulfonated Rhodamines and HaloTag

AbstractDisulfonated rhodamines are photostable and bright dyes widely used in life science and optical microscopy. However, di‐sulfonated dyes were considered cell impermeable and not applicable in living cells. We challenged this assumption with 5 most popular rhodamines (Rho) having two carboxylic acid residues, versatile sulfonation patterns and emitting green (AS488), yellow (Rho530), orange (Rho565) and red (Rho590 and STAR RED) light. The probes comprising one rhodamine entity and a HaloTagTM amine (O2) ligand (x) were prepared and applied for labeling of living, Vimentin‐Halo (VIM‐Halo) expressing U‐2 OS cells. Surprisingly, we observed specific and bright staining with simplest compounds Rho590‐x, Rho565‐x and Rho530‐x bearing two negative charges; they performed well also in stimulated emission depletion (STED) microscopy. Specific staining and red shifts in absorption and emission bands were observed with other probes having one negative charge; they were prepared by native chemical ligation and esterification.

Triterpenoid esters from Capparis erythrocarpos (Isert), Capparaceae, root bark ameliorates CFA-induced arthritis

The root bark of Capparis erythrocarpos (CERB) is employed to treat rheumatoid arthritis (RA) in Africa, particularly in Ghana. However, there was no isolation and characterization of the bioactive constituents responsible for the pharmacological actions of this plant. The aim of this study is to isolate, characterize and evaluate the anti-arthritic activity of the constituents of CERB. CERB was soxhleted and partitioned into various fractions. The constituents were isolated using column chromatography and characterized by 1D and 2D NMR spectroscopy. The precise carboxylic acid residues of the esters were determined using saponification, derivatization and GC–MS analysis. Anti-arthritic activity was evaluated in the CFA-induced arthritic model. Two triterpenoid esters namely, sitosterol 3-hexadecanoate or sitosterol 3-palmatate (1) and sitosterol 3-tetradecanoate or sitosterol 3-myristate (2) in addition to beta sitosterol (3) were isolated and characterized. Compounds 1 and 2 administered at 3 µmol/kg (p.o.) produced anti-inflammatory activity (P < 0.0001) of 31.02 and 39.14% respectively, in addition to arthritic score index (P < 0.0001) of 1.600 ± 0.2449 and 1.400 ± 0.2449 against CFA-induced arthritis which are equivalent to those of the standard drug, diclofenac sodium (DS), 3 µmol/kg (p.o.), (30.79% anti-inflammatory activity and 1.800 ± 0.3742 arthritic score index). The compounds produced similar anti-inflammatory effects as DS. Also, radiographical and histopathological studies showed that, the compounds and DS protected against bone destruction, inflammatory cells invasion into interstitial spaces and synovial liner hyperplasia of the joints. This is the first study to report the characterization of the constituents of C. erythrocarpos in addition to anti-arthritic activity of sitosterol 3-palmatate and sitosterol 3-myristate. These results provide the missing link between the chemistry and the pharmacological activities of C. erythrocarpos. The isolates also offer a different class of molecule which could provide alternative treatment for RA.

Key interactions convert amino acid side chains into strong acids and bases in the active sites of enzymes.

Enzymes catalyze reactions under mild conditions that might otherwise require extreme conditions such as high temperature or strong acid or base. To achieve this, amino acid side chains that are weak Brønsted acids or bases in the free amino acid become strong acids and bases in the active sites of many enzymes. Here we report on a set of 30 enzymes that represent all six major EC classes and a variety of different folds for which experimental studies of the mechanistic roles of the catalytic residues have been reported in the literature. Using macromolecular electrostatics techniques, it is shown that the catalytic aspartate and glutamate residues are strongly coupled to at least one other aspartate or glutamate residue, and often to multiple other carboxylate residues, with intrinsic pKa differences less than 1 pH unit. Sometimes these catalytic acidic residues are also coupled to a histidine residue, such that the intrinsic pKa of the acidic residue is higher than that of the histidine. Most catalytic lysine residues studied here are strongly coupled to tyrosine or cysteine residues, wherein the intrinsic pKa of the anion-forming residue is higher than that of the lysine. Some catalytic lysines are also coupled to other lysines with intrinsic pKa differences within 1 pH unit. Some general principles about the design of enzyme active sites are presented. These principles have significant implications for the engineering of novel enzymes. Supported by NSF CHE-1905214 (MJO).

Graphene oxide-mediated copper reduction allows comparative evaluation of oxygenated reactive residues exposure on the materials surface in a simple one-step method

Graphene Oxide (GO) is the oxidized form of graphene rich in surface groups comprising carbonyl, carboxyl, hydroxyl, and epoxy residues. The solubility in water makes GO an ideal material in the biomedical field though the plethora of synthesis methods available can modify the balance of oxygen groups and, consequently, the effects on eukaryotic and prokaryotic cells. For this reason, GO materials are always characterized with spectroscopic methods such as X-ray photoelectron and Fourier-transform Infrared spectroscopy. However, these techniques have some limitations, being disruptive and not clearly indicating oxygen functionalities available to react with polymers or biological media.In this work, we exploit GO reactivity with copper ions to develop a colorimetric method for the facile evaluation of surface oxidation degree and accessibility in polymeric samples. In the presence of GO, Cu2+ is reduced to Cu1+ and can react with bicinchoninic acid and induce light absorption at 562 nm. We observed that this reaction is dependent both on concentration and oxidation degree, and can be used to estimate GO exposure in thick composite samples. This technique will be fundamental in the future for scaffold characterization in tissue engineering and all the surface science studies analyzing GO-related materials' interactions with biological entities.

Reactive fragments targeting carboxylate residues employing direct to biology, high-throughput chemistry.

The screening of covalent or 'reactive' fragment libraries against proteins is becoming an integral approach in hit identification, enabling the development of targeted covalent inhibitors and tools. To date, reactive fragment screening has been limited to targeting cysteine residues, thus restricting applicability across the proteome. Carboxylate residues present a unique opportunity to expand the accessible residues due to high proteome occurrence (∼12%). Herein, we present the development of a carboxylate-targeting reactive fragment screening platform utilising 2-aryl-5-carboxytetrazole (ACT) as the photoreactive functionality. The utility of ACT photoreactive fragments (ACT-PhABits) was evaluated by screening a 546-membered library with a small panel of purified proteins. Hits identified for BCL6 and KRASG12D were characterised by LC-MS/MS studies, revealing the selectivity of the ACT group. Finally, a photosensitised approach to ACT activation was developed, obviating the need for high energy UV-B light.

Highly compressible composite aerogels constructed by coaxial electrospun fibres and graphene for water sterilization

The electrospun fibres/graphene composite aerogels were assembled with the addition of amino trimethylene phosphonic acid (ATMP). Coaxial electrospinning was employed to attach nanosized-zinc pyrithione, a broad-spectrum biocide, on polyacrylonitrile (PAN) fibre surfaces. Reaction between ATMP and graphene oxide promoted the crosslinking structure of graphene-based aerogels, while producing antibacterial quaternary ammonium and attaching phosphonic acid groups to chelate the metal ions. The addition of the electrospun fibres in the composite aerogels improved the compressive stress at 50% strain by 540% upon the heat treatment at 200 °C, while the sterilization ratio of E. coli reached 100%. The heat treatment was critical for the mechanical properties of the composite aerogels because the linear chains of PAN were turned into rigid ladder polymer upon cyclization, while covalent interaction was introduced between residual carboxyl groups on graphene layers and CN groups of cyclized PAN. The electrospun fibres/graphene composite aerogels can be effectively applied to remove pathogenic bacteria, organic dyes and heavy metal ions in polluted water.

Effect of meso-substituent and solvent nature on spectral properties, pH-stability and affinity to blood transport proteins of BODIPY dyes

The paper is focused on a comparative analysis of the structural and solvation factors on the spectral properties, pH-stability and lipophilicity of BODIPY biomarkers containing in meso-position methyl group, carboxylic acid residues and their esters. The affinity of meso-BODIPYs to blood transport proteins was studied. Dyes intensely absorb (ε ∼ 45000–90000) and fluoresce (to φ ∼ 100 %) in the range of 493–504 and 508–520 nm, respectively. meso-substitution causes a hypsochromic shift (by ∼4–11 nm) of the maximum of the intense absorption band and a noticeable increase of the Stokes shift (up to ∼1.7–2.6 times) of BODIPYs compared to the meso-unsubstituted analog. It has been shown that the introduction of a carboxyl group into the BODIPY meso-position significantly (by a factor of ∼2) increases the hydrophilicity of the compounds, and the presence of ester groups in the structure leads to an increase of the hydrophobicity of the luminophores by a factor of ∼1.3 compared to the meso-unsubstituted dye. It has been demonstrated that compounds are stable in a wide pH range and exhibit intense fluorescence (to φ ∼ 80 %), while carboxyl BODIPYs can be considered as pH sensors for alkaline media. Introducing carboxylic acid residues and their esters into the meso-position of BODIPY is an excellent way to increase affinity dyes to biostructures, including blood transport proteins.

Ultrafast Two-Dimensional Infrared Spectroscopy Resolved a Structured Lysine 159 on the Cytoplasmic Surface of the Microbial Photoreceptor Bacteriorhodopsin.

Bacteriorhodopsin (bR) is a light-driven microbial receptor, and lysine 159 (K159) is a charged residue on the cytoplasmic (CP) side of its E-F loop. However, its conformation and function remain unknown due to fast surface dynamics. By utilizing a 13C, 15N-labeled lysine (K) as an isotope probe, we created a network of site-specific amide-I vibrational signatures (backbone carbonyl stretch) to identify the frequency contribution of the labeled residues to the amide-I excitonic band structure. Thus, the red-shifted amide-I frequency in the 13C, 15N-lysine-labeled bR (uK-bR) to the unlabeled bR (WT-bR) could be differentiated and examined by ultrafast two-dimensional vibrational echo infrared (2D IR) spectroscopy. Our results showed that the backbone carbonyl of K159 is located at a high frequency of ca. 1693 cm-1 and has a vibrational excited-state relaxation time shorter than the bulk helical amide-I mode at the same frequency, suggesting that K159 may possess a hydrogen-bonded γ-turn structure with E161, one of the carboxylate residues on the CP surface of bR. The 2D solid-state NMR study of uK-bR also revealed conformational dependent lysine residues, from which K159 was found to involve the turn motif. This γ-turn structure maintained by K159 may help to stabilize the E-F loop and support E161 in attracting protons from the bulk during the late stage of the bR photocycle. The combined spectroscopic approach illustrated in this work may be applied to map residue-specific local structures and dynamics of other receptors and large proteins.

Proton transfer reactions in donor site mutants of ESR, a retinal protein from Exiguobacterium sibiricum

Light-driven proton transport by microbial retinal proteins such as archaeal bacteriorhodopsin involves carboxylic residues as internal proton donors to the catalytic center which is a retinal Schiff base (SB). The proton donor, Asp96 in bacteriorhodopsin, supplies a proton to the transiently deprotonated Schiff base during the photochemical cycle. Subsequent proton uptake resets the protonated state of the donor. This two step process became a distinctive signature of retinal based proton pumps. Similar steps are observed also in many natural variants of bacterial proteorhodopsins and xanthorhodopsins where glutamic acid residues serve as a proton donor. Recently, however, an exception to this rule was found. A retinal protein from Exiguobacterium sibiricum, ESR, contains a Lys residue in place of Asp or Glu, which facilitates proton transfer from the bulk to the SB. Lys96 can be functionally replaced with the more common donor residues, Asp or Glu. Proton transfer to the SB in the mutants containing these replacements (K96E and K96D/A47T) is much faster than in the proteins lacking the proton donor (K96A and similar mutants), and in the case of K96D/A47T, comparable with that in the wild type, indicating that carboxylic residues can replace Lys96 as proton donors in ESR. We show here that there are important differences in the functioning of these residues in ESR from the way Asp96 functions in bacteriorhodopsin. Reprotonation of the SB and proton uptake from the bulk occur almost simultaneously during the M to N transition (as in the wild type ESR at neutral pH), whereas in bacteriorhodopsin these two steps are well separated in time and occur during the M to N and N to O transitions, respectively.

Effects of Commercial No-Clean Flux on Reliability of Fine Pitch Flip-Chip Package With Solder Bumps and Copper Pillars

In this work, two commercial no clean fluxes, namely, extremely low residue no-clean flux (NCF) (NC-1) and ordinary NCF (NC-2), were used for the preparation of a fine pitch flip-chip package with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.6\,\times \,7.6$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Si die on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17\,\times \,17$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> organic substrate. One water-soluble (WS) flux was also used for comparison. Moisture sensitivity of the package was evaluated using JESD22-A113D (30 °C/60% relative humidity (RH), 192 h, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times $ </tex-math></inline-formula> reflow at 260 °C). Thermal cycling tests were performed following JESD22-A104D (−65 °C to 150 °C). The high-temperature storage life (HTSL) of the packages was investigated using JESD22-A103C (175 °C). Underfill delamination or voids in the package were investigated by confocal scanning acoustic microscopy (C-SAM). Failure characteristics of the packages were also studied using scanning electron microscopy (SEM). After moisture sensitivity level (MSL) test, vehicles prepared by NC-1 and NC-2 showed failure. SEM images revealed severe delamination between underfill and solder mask in the presence of amine/amide and carboxylic acid-based NCF residue. Solder bump crack were found at < 500 cycles for samples prepared with NC-1 which contains tertiary amine and long carbon chain (C8:C10:C12) carboxylic acid-based. However, failure occurred at < 1500 cycles for NC-2 containing secondary amide and shorter carbon chain length (C3) carboxylic acid. Samples prepared using WS did not show any failure for up to 2000 cycles. Thus, NCF-treated assemblies performed poorly in moisture sensitivity and temperature cycling tests.

Ynamide Electrophile for the Profiling of Ligandable Carboxyl Residues in Live Cells and the Development of New Covalent Inhibitors.

Covalent inhibitors with an electrophilic warhead have received considerable attention due to their remarkable pharmacological properties. However, the electrophilic warhead in covalent drugs is often an α, β-unsaturated amide, and the targets are mainly cysteine or lysine residues. Thus, the development of novel electrophiles that can target other amino acids is highly desirable. Ynamide, a useful and versatile building block, is commonly employed in the construction of various compounds in organic synthesis. The performance of this functional group in a proteome-wide environment has been studied here for the first time, and it has been shown that it can efficiently modify carboxyl residues in situ and in vitro. Upon incorporation of this ynamide warhead into the pharmacophores of kinase inhibitors, the resulting compound showed moderate inhibition against the EGFR L858R mutant but not against EGFR WT. This novel electrophilic group can be used in the development of new types of covalent inhibitors.

Development of a β-cyclodextrin-chitosan polymer as active coating for cellulosic surfaces and capturing of microcystin-LR

In the search for more environmentally friendly adsorbent materials, the use of polysaccharides results attractive. Especially, as they can be used as coatings to add functionality to common materials as a new avenue to explore. Their inherent tendency to adsorb into each other is valuable as it adds a variety of functional groups on the outmost surface layer. Our project focuses on the pre-modification of the bio-polymer chitosan (Ch) with a 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) oxidized β-cyclodextrin (Ch-TOCD), which was then adsorbed onto the cellulose nanofibrils (CNF) surface. Furthermore, the mechanism driving the adsorption of the modified chitosan onto the cellulose backbone was studied by using three different Ch-TOCD conjugates possessing different degrees of substitutions. This was conducted to evaluate whether the adsorption was guided by the change of the available electrostatic interactions between the amino (Ch) and the residual carboxyl groups of cellulose or if the adsorption was driven by the dispersive forces of the hydroxyl groups from both polysaccharides. Finally, to assess the viability of the added hydrophobic cavities (Ch-TOCD conjugate), the capture of an amphipathic toxin categorized as a monitored pollutant (microcystin-LR) was followed by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) on a surface level and by High-performance liquid chromatography (HPLC) when the Ch-TOCD coating was applied in CNF beads. Results showed that the adsorption of Ch-TOCD was accomplished at similar levels independent of the degree of substitution. The highest adsorbed amounts of microcystin-LR were 20.5 mg/g on the model coated CNF surface, and 2.36 mg/g on the CNF coated beads. The successful coating of two nanocellulose systems and the positive adsorption of the microcystin suggest a broad-scale application of this bio-based, low energy input coating in high-end fields such as drug delivery, textile, and water restoration.

Effect of aluminum leaching pretreatment on catalytic pyrolysis of metallised food packaging plastics and its linear and nonlinear kinetic behaviour

This research aims to study the effect of aluminum (Al) leaching pre-treatment on the catalytic pyrolysis of metallised food packaging plastics waste (MFPW). The experiments started with removal of Al from MFPW using leaching process to prepare Al-free mixed plastic waste (MPW). The catalytic pyrolysis of MPW over ZSM-5 zeolite catalyst was carried out using thermogravimetric (TG) analysis coupled with FTIR, while GC–MS was used to observe the compounds of the volatile products. The catalytic pyrolysis kinetic behaviour of MPW was studied using the linear and nonlinear isoconversional approaches. The elemental and proximate results showed that MPW is very rich in carbon elements (79 %) and volatile content (99 %). The TG results showed that MPW and ZSM/MPW were fully decomposed in the range of 376–496 °C without any presence of char. Based on TG-FTIR analysis, methane and carboxylic acid residue were the main groups of the synthesized volatile products, whereas nitrous oxide, 1-Butanol, 1-Propene, acetic acid, and formic acid were the major GC compounds. In case of ZSM/MPW, carbon dioxide and acetic acid were the major GC compounds at 5–25 °C/min, triphenylphosphine oxide and Phosphine oxide at 30 °C/min. The kinetic analysis showed that when the activation energies are located in the range 287–297 kJ/mol (MPW) and 153–187 kJ/mol (ZSM/MPW) and KAS, Vyazovkin, and Cai methods are the most suitable models to study pyrolysis kinetic of MPW with R2 > 89. Based on that, leaching and catalytic pyrolysis processes are a highly suggested technology that can be used to convert MFPW into high-added energy and chemical products.

A Review Study of the Influences of Dendrimer Nanoparticles on Stored Platelet in Order to Treat Patients (2001-2020)

Background: Platelets are sensitive to chilling, so the optimal storage temperature for maintaining normal function and structure in platelets is 22-24 °C up to 3-5 days. Introduction: Platelets are important blood cells involved in immunity, inflammation, and thrombosis. Today, platelet products are widely used to prevent bleeding in patients with thrombocytopenia and coagulopathy disorders. As a result, maintaining the quality of these products is very important. Method: In this review study, the reported influences of various dendrimers on platelets from 2001 to 2020 were investigated. Result: The results showed that positively charged dendrimers can cause platelet aggregation and activation during platelet storage time through their amine residues. In addition to surface charge, high generations, molecular weight and concentration are not recommended in the field of platelet storage and treatment. In contrast, negatively charged dendrimers, usually used at lower generations with proper molecular weight, lower size (less than 100 nm) and their carboxyl residues, cannot induce adverse effects on platelets during storage time. In addition, the results of this study revealed that PEGylation of dendrimers and platelets can improve platelet storage conditions. Conclusion: As anionic dendrimers can improve platelet storage time without inducing significant changes in morphology and function of platelets, they are recommended in the field of platelet storage and treatment.

Electrostatic Fingerprints of Catalytically Active Amino Acids in Enzymes

The computed electrostatic and proton transfer properties are studied for 20 enzymes that represent all six major EC classes and a variety of different folds. The properties of aspartate, glutamate, and lysine residues that have been previously experimentally determined to be catalytically active are reported. All catalytic aspartate and glutamate residues studied here are strongly coupled to at least one other aspartate or glutamate residue and often to multiple other carboxylate residues with intrinsic pKa differences less than 1 pH unit. Sometimes these catalytic acidic residues are also coupled to a histidine residue, such that the intrinsic pKa of the acidic residue is higher than that of the histidine. All catalytic lysine residues studied here are strongly coupled to tyrosine or cysteine residues, wherein the intrinsic pKa of the anion‐forming residue is higher than that of the lysine. Some catalytic lysines are also coupled to other lysines with intrinsic pKa differences within 1 pH unit. Some evidence of the possible types of interactions that facilitate nucleophilicity is discussed. The interactions reported here provide important clues about how side chain functional groups that are weak Br⊘nsted acids or bases for the free amino acid in solution can become strong acids, bases or nucleophiles in the enzymatic environment. Such interactions are important considerations in enzyme design.