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•A blend of toluene and NMP effectively detaches bitumen from siliceous surfaces.•Hybrid solvent dissolves the asphaltene agglomerates within aged bitumen.•Hybrid solvent supersedes ...bitumen compounds for adsorption to silica.•Hybrid blend of toluene and NMP is a more effective desorbent than toluene alone.
This paper studies the role of 1-methyl-2-pyrrolidone (NMP) additive to enhance the desorption power of toluene to detach the bitumen from siliceous surfaces. The latter desorption is critical for successful recycling of old asphalt roads where aged bitumen is expected to come off the stones and blend with virgin bitumen used in construction of new roads. Toluene, a documented neurotoxin, has been commonly used to separate aged bitumen from siliceous surface; increasing toluene desorption power and dosage efficiency allows reduced application rate leading to significant environmental and economic benefits. Here, we used the laboratory experiments and computational modeling to understand mechanism of desorption afforded by a hybrid solvent made from blends of toluene and NMP. Our results showed the hybrid solvent interacts with both bitumen and siliceous surfaces; this in turn allows the solvent not only dissolve the asphaltene agglomerates in aged bitumen, but also supersede bitumen compounds for adsorption to silica. Our modeling revealed the hybrid solvent creates an amphiphile that is both able to attach to the asphaltene molecules and interact with polar water molecules, thus making a monolithic cluster that is easy to detach from the siliceous surface under hydraulic pressure. This was further evidenced in a high reduction in the shear-thinning rate of bitumen-silica matrix when hybrid solvent was introduced; for instance, in the case of severely aged bitumen bonded to silica, shear-thinning rate reduced by 60% when hybrid solvent was introduced. Study outcomes provide insights into the merits of using hybrid solvent for desorption as well as its working mechanism. Such insights set a path for future efforts in pavement recycling and promote resource conservation and sustainable development.
•Comprehensive rejuvenation increases both crossover modulus and crossover frequency.•Bio-rejuvenator de-agglomerates self-assembled oxidized asphaltenes.•Bio-rejuvenator molecules have a peptizing ...effect on oxidized asphaltene molecules.•Bio-rejuvenator reduces the intensity of radial distribution function of asphaltenes in heptane.
This paper introduces a new bio-rejuvenator made from a blend of high-protein algae and high-lipid animal manure and studies its interaction with aged bitumen molecules to revitalize aged asphalt. True revitalization requires restoring not only the chemical balance but also the molecular conformation. Therefore, rejuvenators should be able to de-agglomerate oxidized asphaltenes while compensating for components that are lost during aging. This study uses a balanced feedstock to control the composition and concentration of active molecules in a rejuvenator to increase its efficiency. To do so, a balanced combination of high-protein algae and high-lipid manure were used to synthesize bio-rejuvenator having different concentration of straight chain hydrocarbons and aromatic compounds, with the former helping to restore chemical balance, and the latter working to de-agglomerate oxidized asphaltene. This in turn can restore aged bitumen's molecular conformation, leading to restoration of its physicochemical and rheological properties. The study results showed that bio-rejuvenator produced from the algae-manure balanced feedstock was more effective rejuvenator than using either of algae or manure solely. The superiority of rejuvenator made by co-liquefaction of a balanced feedstock verified by comparing its dosage efficiency with that of its counterparts made from isolated bio-mass sources. The comparison was done based on the extent of increase in crossover modulus and crossover frequency of an aged bitumen doped with a constant dosage of each rejuvenator with co-liquified scenario showing a much higher increase than other scenarios. Molecular dynamics simulation results revealed that latter bio-rejuvenator’s molecules have a peptizing effect on oxidized asphaltene molecules leading to a significant decrease in the radial distribution function of oxidized asphaltene molecules restoring their molecular conformation. This in turn leads to revitalizing aged asphalt physio-chemical properties to enable reuse and recycling of aged asphalt composites and improve recycling of asphalt pavements to promote sustainability.
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•A hybrid bio-oil (HY) introduced as a multifunctional agent for asphalt recycling.•HY can desorb the severely aged bitumen from siliceous aggregates.•HY peptizes the bitumen ...compounds within the bituminous mixture.•HY rejuvenates the aged bitumen while ensures the durability.
This paper reveals the working mechanisms of a hybrid bio-oil (HY) which plays as a multifunctional agent by desorbing bitumen molecules from siliceous surfaces and peptizing them within the bitumen colloidal structure. This in turn counteracts some of the negative effects of bitumen’s aging. Recently, it was found that aging increases associated interfacial bonds at the bitumen-stone interface and promotes self-association of bitumen molecules. These negatively affects bitumen extraction from siliceous substrates, such as shale, and bitumen recycling from aged roads, airports, bridge decks, and roofs to name a few. Abovementioned extraction and recycling involve detachment of molecules of aged bitumen from stone aggregates and adequately peptizing them within the bitumen matrix. Here, we used molecular modeling and laboratory experiments to elucidate how HY facilitates the detachment and subsequent peptizing of bitumen molecules while ensures the durability. Our modeling showed that HY has two important properties: HY is a strong peptizing agent due to its interactions with molecules in aged bitumen; and HY supersedes molecules of bitumen for adsorption to siliceous surface due to HY’s higher affinity toward silica active sites. According to our results, heterocyclic HY molecules (1-butyl-Piperidine and N-methyl-2-Pyrrolidone) lead by neutralizing the polar interactions between oxidized bitumen and silica, thus providing an opportunity for other HY molecules to intercalate into the interface and replace the oxidized bitumen on silica. Thus, HY makes a promising rejuvenator, which can revitalize aged bitumen by simultaneously desorbing and peptizing aged bitumen molecules. HY’s preferential adsorption to silica combined with its high resistance to be replaced by water further helps improve the resistance of revitalized bitumen to moisture-induced damages, evidenced in our experiment. Therefore, HY can be a promising multifunctional bio-agent for extraction and recycling of bitumen to promote environmental sustainability and resource conservation.
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•Effects of rejuvenators on durabiity of bitumen should be factored in selection criteria.•Crossover modulus & crossover frequency detects dissociation & peptizing of ...nanoaggregates.•A Chemistry-informed design of rejuvenators ensure effective restoration & durability.
Recycling of oxidized bitumen requires proper dissociation and peptizing of bitumen nanoaggregates referred to as rejuvenation. While there are many modifiers or so-called rejuvenators to perform the latter dissociation and peptizing actions, some of them compromise durability of recycled bitumen by inadvertently increasing its susceptibility to moisture damage. Here, we study moisture resistance of laboratory aged bitumens for which a synthesized rejuvenator referred to as Switein was used. In this study, Switein is prepared from a blend of lipid and protein via co-processing of food waste and animal waste through thermochemical conversion. Study results showed that the rejuvenator effectively restored the crossover modulus properties of all aged bitumens regardless of their aging levels. Restoration effectiveness was also verified by Glover-Rowe (G-R) parameters and healing indexes. A durability comparison showed that the resistance to moisture damage in bitumens rejuvenated with Switein was much higher than those rejuvenated by another bio-based rejuvenator. It should be noted that both rejuvenators were effective to restore physio-chemical and rheological properties of aged bitumens. This in turn highlights the importance of factoring in durability effects of rejuvenators among their selection criteria. The study outcomes emphasize the significance of using a chemistry-informed design for bitumen modifiers to ensure not only proper restoration is achieved, but also durability is not compromised.
Nucleoprotein is a conserved structural protein of SARS-CoV-2, which is involved in several functions, including replication, packaging, and transcription. In this research, 21 antiviral peptides ...that are known to have inhibitory function against nucleoprotein in several other viruses, were screened computationally against the nucleoprotein of SARS-CoV-2. The complexes of five best performing peptides (AVP1142, AVP1145, AVP1148, AVP1150, AVP1155) with nucleoprotein were selected for subsequent screening via 5 ns molecular dynamics (MD) simulation. Two peptides, namely AVP1145 and AVP1155, came out as promising candidates and hence were selected for 200 ns MD simulation for further validation, incorporating a DMPC-based membrane environment. In the long MD simulation, both AVP1155 and AVP1145 utilized multiple residues—mainly aromatic, acidic, and nonpolar residues—as interacting points to remain in contact with the nucleoprotein and formed predominantly hydrogen bonds along with hydrophobic and electrostatic interactions. However, AVP1155 proved to be superior to AVP1145 when its complex with nucleoprotein was analyzed in terms of root-mean-square deviation, root-mean-square fluctuation, radius of gyration, solvent accessible surface area and free energy landscape. In a nutshell, the findings of this research may guide future studies in the development of selective peptide inhibitors of SARS-CoV-2 nucleoprotein.
Over 50 peptides, which were known to inhibit SARS-CoV-1, were computationally screened against the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2. Based on the binding affinity and ...interaction, 15 peptides were selected, which showed higher affinity compared to the α-helix of the human ACE2 receptor. Molecular dynamics simulation demonstrated that two peptides, S2P25 and S2P26, were the most promising candidates, which could potentially block the entry of SARS-CoV-2. Tyr489 and Tyr505 residues present in the “finger-like” projections of the RBD were found to be critical for peptide interaction. Hydrogen bonding and hydrophobic interactions played important roles in prompting peptide–protein binding and interaction. Structure–activity relationship indicated that peptides containing aromatic (Tyr and Phe), nonpolar (Pro, Gly, Leu, and Ala), and polar (Asn, Gln, and Cys) residues were the most significant contributors. These findings can facilitate the rational design of selective peptide inhibitors targeting the spike protein of SARS-CoV-2.
Computer-aided drug screening by molecular docking, molecular dynamics (MD) and structural-activity relationship (SAR) can offer an efficient approach to identify promising drug repurposing ...candidates for COVID-19 treatment. In this study, computational screening is performed by molecular docking of 1615 Food and Drug Administration (FDA) approved drugs against the main protease (Mpro) of SARS-CoV-2. Several promising approved drugs, including Simeprevir, Ergotamine, Bromocriptine and Tadalafil, stand out as the best candidates based on their binding energy, fitting score and noncovalent interactions at the binding sites of the receptor. All selected drugs interact with the key active site residues, including His41 and Cys145. Various noncovalent interactions including hydrogen bonding, hydrophobic interactions, pi-sulfur and pi-pi interactions appear to be dominant in drug-Mpro complexes. MD simulations are applied for the most promising drugs. Structural stability and compactness are observed for the drug-Mpro complexes. The protein shows low flexibility in both apo and holo form during MD simulations. The MM/PBSA binding free energies are also measured for the selected drugs. For pattern recognition, structural similarity and binding energy prediction, multiple linear regression (MLR) models are used for the quantitative structural-activity relationship. The binding energy predicted by MLR model shows an 82% accuracy with the binding energy determined by molecular docking. Our details results can facilitate rational drug design targeting the SARS-CoV-2 main protease.
Communicated by Ramaswamy H. Sarma
This paper examines the durability of restored aged asphalt in terms of its susceptibility to moisture and aging. The study is motivated by the increasing use of modifiers called rejuvenators that ...are added to paving mixtures containing reclaimed asphalt pavements to restore the original rheological properties of asphalt binder that have been lost during service life. Although several test methods have been proposed to quantify the restoration capability of rejuvenators, not much attention has been given to the side-effects that the rejuvenators may impart to the resulting mix. Due to the specific chemical composition of certain rejuvenators, they may negatively impact the durability of the mixture, especially pertaining to its resistance to moisture damage and aging. This paper examines several rejuvenators that are all effective at restoring aged asphalt binder’s rheological properties, to highlight plausible side effects that may be overlooked when selection criteria are based solely on the restoration capacity of rejuvenators. Our laboratory experiments and computational analysis geared toward the use of rheometry and density functional theory showed that while all studied rejuvenators restored the rheological properties of aged asphalt binders, they had very different durability in terms of resistance to aging and moisture damage. Results obtained from the dynamic shear rheometer showed the rejuvenators with the highest restoration capacity did not have the best durability. Computational analysis showed that while the restoration capacity of rejuvenators is related to their penetration into and peptizing of asphaltene nanoaggregates, durability is mainly related to their polarizability values. Rejuvenators with lower polarizability showed better resistance to aging and moisture damage. The outcome of the study facilitates production of effective rejuvenators without compromising the long-term durability of restored asphalt binder. It also helps road authorities develop selection metrics that account for durability along with rheological properties, to prevent non-durable rejuvenators from entering the market. Accordingly, the study results promote sustainability and resource conservation by providing an in-depth understanding of the relation between rejuvenators’ chemical structure and the durability of restored aged asphalt binder.
Durability of rejuvenated pavements can be compromised if moisture-susceptible rejuvenators are used to restore rheological properties of aged asphalt. Display omitted
SARS-CoV-2 virus outbreak poses a major threat to humans worldwide due to its highly contagious nature. In this study, molecular docking, molecular dynamics, and structure-activity relationship are ...employed to assess the binding affinity and interaction of 76 prescription drugs against RNA dependent RNA polymerase (RdRp) and Main Protease (Mpro) of SARS-CoV-2. The RNA-dependent RNA polymerase is a vital enzyme of coronavirus replication/transcription complex whereas the main protease acts on the proteolysis of replicase polyproteins. Among 76 prescription antiviral drugs, four drugs (Raltegravir, Simeprevir, Cobicistat, and Daclatasvir) that are previously used for human immunodeficiency virus (HIV), hepatitis C virus (HCV), Ebola, and Marburg virus show higher binding energy and strong interaction with active sites of the receptor proteins. To explore the dynamic nature of the interaction, 100 ns molecular dynamics (MD) simulation is performed on the selected protein-drug complexes and apo-protein. Binding free energy of the selected drugs is performed by MM/PBSA. Besides docking and dynamics, partial least square (PLS) regression method is applied for the quantitative structure activity relationship to generate and predict the binding energy for drugs. PLS regression satisfactorily predicts the binding energy of the effective antiviral drugs compared to binding energy achieved from molecular docking with a precision of 85%. This study highly recommends researchers to screen these potential drugs in vitro and in vivo against SARS-CoV-2 for further validation of utility.
Communicated by Ramaswamy H. Sarma
The receptor-binding domain (RBD) of SARS-CoV-2 spike (S) protein plays a vital role in binding and internalization through the alpha-helix (AH) of human angiotensin-converting enzyme 2 (hACE2). ...Thus, it is a potential target for designing and developing antiviral agents. Inhibition of RBD activity of the S protein may be achieved by blocking RBD interaction with hACE2. In this context, inhibitors with large contact surface area are preferable as they can form a potentially stable complex with RBD of S protein and would not allow RBD to come in contact with hACE2. Peptides represent excellent features as potential anti-RBD agents due to better efficacy, safety, and tolerability in humans compared to that of small molecules. The present study has selected 645 antiviral peptides known to inhibit various viruses and computationally screened them against the RBD of SARS-CoV-2 S protein. In primary screening, 27 out of 645 peptides exhibited higher affinity for the RBD of S protein compared to that of AH of the hACE2 receptor. Subsequently, AVP1795 appeared as the most promising candidate that could inhibit hACE2 recognition by SARS-CoV 2 as was predicted by the molecular dynamics simulation. The critical residues in RBD found for protein-peptide interactions are TYR 489, GLY 485, TYR 505, and GLU 484. Peptide-protein interactions were substantially influenced by hydrogen bonding and hydrophobic interactions. This comprehensive computational screening may provide a guideline to design the most effective peptides targeting the spike protein, which could be studied further in vitro and in vivo for assessing their anti-SARS CoV-2 activity.
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•Antiviral peptides can be a promising therapeutic strategy to inhibit SARS-CoV-2.•645 antiviral peptides were screened against RBD of the spike protein of SARS-CoV-2.•150 ns molecular dynamics simulation has been performed for peptide-protein complexes.•Two promising peptides were found which show significant binding and interactions with RBD of SARS CoV-2.
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