How to perceive and map the synergy between CO2 and air pollutants: Observation, measurement, and validation from a case study of China.

Cities occupy a central position in addressing climate change and promoting sustainable regional development. Synergistic control of urban gas emissions at the city level is one of the main issues typically explored. The confounding effect and the interactions between the urban indicators of population and area have been ignored in previous studies. In this study, we examined the spatial distribution characteristics and synergy between greenhouse gases (CO2) and air pollutants (SO2 and NOX) using spatial population and gas emission data. By upgrading the city clustering algorithm (CCA), we established a method for defining active areas of gas emissions (spatial element-coupled clustering, SECC) and identified active areas of gas emissions in China. In this study, we created a research framework that can simultaneously consider the effects of population and area, as well as the possible interactions between these indicators in active areas. The superlinear scaling relationship between the above three gases was revealed at the active zone level, and the existence of synergy between the emission patterns of the three gases was confirmed. Via further model application, we measured the synergistic efficiency of the three gases. It was found that for every 1% increase in SO2 and NOX in an active zone, CO2 increases by 0.86%. In this study, we explored a new perspective and approach to explain the synergy between greenhouse gases and air pollutants. This is essential to promote national competition among cities to achieve synergistic control of CO2 and local air pollutants.

Synthesis of Cyclic Peptides in SPPS with Npb-OH Photolabile Protecting Group.

Significant efforts have been made in recent years to identify more environmentally benign and safe alternatives to side-chain protection and deprotection in solid-phase peptide synthesis (SPPS). Several protecting groups have been endorsed as suitable candidates, but finding a greener protecting group in SPPS has been challenging. Here, based on the 2-(o-nitrophenyl) propan-1-ol (Npp-OH) photolabile protecting group, a structural modification was carried out to synthesize a series of derivatives. Through experimental verification, we found that 3-(o-Nitrophenyl) butan-2-ol (Npb-OH) had a high photo-release rate, high tolerance to the key conditions of Fmoc-SPPS (20% piperidine DMF alkaline solution, and pure TFA acidic solution), and applicability as a carboxyl-protective group in aliphatic and aromatic carboxyl groups. Finally, Npb-OH was successfully applied to the synthesis of head-tail cyclic peptides and side-chain-tail cyclic peptides. Moreover, we found that Npb-OH could effectively resist diketopiperazines (DKP). The α-H of Npb-OH was found to be necessary for its photosensitivity in comparison to 3-(o-Nitrophenyl)but-3-en-2-ol (Npbe-OH) during photolysis-rate verification.

Design, Synthesis and Evaluation of 3-Substituted Coumarin Derivatives as Anti-inflammatory Agents.

Coumarin moiety has garnered momentous attention especially in the design of compounds with significant biological activities. In this work, a series of 3-substituted coumarin derivatives 6a-6l were synthesized and fully characterized. Most of the compounds could obviously inhibit the activity of cyclooxygenase-1 (COX-1) at the concentration of 10 µM. Besides, 6h and 6l exhibited highest inhibitory effects against COX-2 with inhibition rates of 33.48 and 35.71%, respectively. Detailed structure-activity relationships (SARs) were also discussed. In vivo studies, 6b, 6i and 6l could remarkably repress the xylene-induced ear swelling in mice at the dose of 20 mg/kg. Especially, 6l seemed to be the most effective compound at the dose of 10 mg/kg, displaying favorable anti-inflammatory activity comparable to indomethacin. All of these findings suggested that 6l might be utilized as a candidate for the treatment of inflammatory diseases.

Design, Synthesis and Preliminary Biological Evaluation of Benzylsulfone Coumarin Derivatives as Anti-Cancer Agents.

In this work, a series of benzylsulfone coumarin derivatives 5a-5o were synthesized and characterized. Kinase inhibitory activity assay indicated that most of the compounds showed considerable activity against PI3K. Anti-tumor activity studies of the active compounds were also carried out in vitro on the Hela, HepG2, H1299, HCT-116, and MCF-7 tumor cell lines by MTS assay. The structure-activity relationships (SARs) of these compounds were analyzed in detail. Compound 5h exhibited the most potent activities against the mentioned cell lines with IC50 values ranging from 18.12 to 32.60 µM, followed by 5m with IC50 values of 29.30-42.14 µM. Furthermore, 5h and 5m clearly retarded the migration of Hela cells in vitro. Next, an in silico molecular docking study was conducted to evaluate the binding models of 5h and 5m towards PI3Kα and PI3Kß. Collectively, the above findings suggested that compounds 5h and 5m might be promising PI3K inhibitors deserving further investigation for cancer treatment.

Design, Synthesis and Preliminary Biological Evaluation of Novel Benzyl Sulfoxide 2-Indolinone Derivatives as Anticancer Agents.

In this work, a series of novel benzyl sulfoxide 2-indolinone derivatives was designed and synthesized as potent anticancer agents. Tyrosine kinase inhibitory activity assay indicated that most of the compounds showed significant activity. The in vitro antiproliferative activity of these compounds was further investigated against five human cancer cell lines (HeLa, HepG2, MCF-7, SCC-15, and A549). Several compounds exhibited evident activities. Among them, (Z)-3-(((4-bromobenzyl)sulfinyl)methylene)indolin-2-one (6j) and (Z)-3-((benzylsulfinyl)methylene)-5-bromoindolin-2-one (6o) were found to be effective tyrosine kinase inhibitors (IC50 = 1.34 and 2.69 µM, respectively) in addition to having noteworthy antitumor potential (the average IC50 value of 6j or 6o was less than 40 µM). This class of novel derivatives has promising potential for further development as anticancer agents.

Synthesis and Evaluation of Novel Benzofuran Derivatives as Selective SIRT2 Inhibitors.

A series of benzofuran derivatives were designed and synthesized, and their inhibitory activites were measured against the SIRT1-3. The enzymatic assay showed that all the compounds showed certain anti-SIRT2 activity and selective over SIRT1 and SIRT3 with IC50 (half maximal inhibitory concentration) values at the micromolar level. The preliminary structure-activity relationships were analyzed and the binding features of compound 7e (IC50 3.81 µM) was predicted using the CDOCKER program. The results of this research could provide informative guidance for further optimizing benzofuran derivatives as potent SIRT2 inhibitors.

Design and Synthesis of 3-(2H-Chromen-3-yl)-5-aryl-1,2,4-oxadiazole Derivatives as Novel Toll-like Receptor 2/1 Agonists That Inhibit Lung Cancer In Vitro and In Vivo.

Toll-like receptor (TLR) 2 is a transmembrane receptor that participates in the innate immune response by forming a heterodimer with TLR1 or TLR6. TLR2 agonists play an important role in tumor therapy. Herein, we synthesized a series of 3-(2H-chromen-3-yl)-5-aryl-1,2,4-oxadiazole derivatives and identified WYJ-2 as a potent small and selective molecule agonist of TLR2/1, with an EC50 of 18.57 ± 0.98 nM in human TLR2 and TLR1 transient-cotransfected HEK 293T cells. WYJ-2 promoted the formation of TLR2/1 heterodimers and activated the nuclear factor kappa B (NF-κB) signaling pathway. Moreover, our study indicated that WYJ-2 could induce pyroptosis in cancer cells, mediated by activating the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome. WYJ-2 exhibited effective anti-non-small cell lung cancer (NSCLC) activity in vitro and in vivo. The discovery that activating TLR2/1 induces pyroptosis in cancer cells may highlight the prospects of TLR2/1 agonists in cancer treatment in the future.

Design, synthesis, biological evaluation and in silico studies of novel quinoline derivatives as potential radioprotective molecules targeting the TLR2 and p53 pathways.

Ionizing radiation in space, radiation devices or nuclear disasters are major threats to human health and public security. In this paper, in order to find the potential novel compounds decreasing the radiation-induced damage by targeting p53 apoptosis pathway and TLR2 passway, a series of novel quinoline derivatives were designed, synthesized, and evaluated their biological activities. Most of the synthesized compounds showed significant radioprotective effects in vitro, and the compound 5 has the best performance. Therefore, we verified its radioprotective activity in vivo and investigated the mechanism of its excellent activity. The results in vivo indicated that compound 5 not only markedly enhanced the survival rate (80 %) of mice 30 days after lethal exposure to irradiation, but also significantly reduced the radiation-induced damage to haematopoietic system and intestinal tissue of mice. The mechanistic studies indicated that compound 5 acted on the p53 pathway to reduce radiation-induced cell apoptosis and at the same time stimulated TLR2 to up-regulate the expressions of radiation protection factors. Molecular dynamics study shows that compound 5 would effectively bind to the TLR2 protein and further revealed the binding mechanism. Taken together, all the findings of our study demonstrate the quinoline derivative 5 is a potent radioprotective compound, which holds a great therapeutic potential for further development.

Radioprotective effectiveness of a novel delta-tocotrienol prodrug on mouse hematopoietic system against 60Co gamma-ray irradiation through inducing granulocyte-colony stimulating factor production.

Considering the increasing risk of nuclear attacks worldwide, the development of develop potent and safe radioprotective agents for nuclear emergencies is urgently needed. γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have demonstrated a potent radioprotective effect by inducing the production of granulocyte-colony stimulating factor (G-CSF) in vivo. However, their application is limited because of their low bioavailability. The utilization of ester prodrugs can be an effective strategy for modifying the pharmacokinetic properties of drug molecules. In this study, we initially confirmed that DT3 exhibited the most significant potential for inducing G-CSF effects among eight natural vitamin E homologs. Consequently, we designed and synthesized a series of DT3 ester and ether derivatives, leading to improved radioprotective effects. The metabolic study conducted in vitro and in vivo has identified DT3 succinate 5b as a prodrug of DT3 with an approximately seven-fold higher bioavailability compared to DT3 alone. And DT3 ether derivative 8a were relatively stable and approximately 4 times more bioavailable than DT3 prototype. Furthermore, 5b exhibited superior ability to mitigate radiation-induced pancytopenia, enhance the recovery of bone marrow hematopoietic stem and progenitor cells, and promote splenic extramedullary hematopoiesis in sublethal irradiated mice. Similarly, 8a shown potential radiation protection, but its radiation protection is less than DT3. Based on these findings, we identified 5b as a DT3 prodrug, and providing an attractive candidate for further drug development.

Induction of activation of the antioxidant response element and stabilization of Nrf2 by 3-(3-pyridylmethylidene)-2-indolinone (PMID) confers protection against oxidative stress-induced cell death.

The antioxidant response elements (ARE) are a cis-acting enhancer sequence located in regulatory regions of antioxidant and detoxifying genes. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a member of the Cap 'n' Collar family of transcription factors that binds to the ARE and regulates the transcription of specific ARE-containing genes. Under oxidative stress, Nrf2/ARE induction is fundamental to defense against reactive oxygen species (ROS) and serves as a key factor in the protection against toxic xenobiotics. 3-(3-Pyridylmethylidene)-2-Indolinone (PMID) is a derivative of 2-indolinone compounds which act as protein kinase inhibitors and show anti-tumor activity. However, the role of PMID in the oxidative stress remains unknown. In the present study, we showed that PMID induced the activation of ARE-mediated transcription, increased the DNA-binding activity of Nrf2 and then up-regulated the expression of antioxidant genes such as HO-1, SOD, and NQO1. The level of Nrf2 protein was increased in cells treated with PMID by a post-transcriptional mechanism. Under CHX treatment, the stability of Nrf2 protein was enhanced by PMID with decreased turnover rate. We showed that PMID reduced the ubiquitination of Nrf2 and disrupted the Cullin3 (Cul3)-Keap1 interaction. Furthermore, cells treated with PMID showed resistance to cytotoxicity by H(2)O(2) and pro-oxidant 6-OHDA. PMID also up-regulated the antioxidant level in BALB/c mice. Taken together, the compound PMID induces the ARE-mediated gene expression through stabilization of Nrf2 protein and activation of Nrf2/ARE pathway and protects against oxidative stress-mediated cell death.

A perception of the nexus "resistance, recovery, resilience" of vegetations responded to extreme precipitation pulses in arid and semi-arid regions: A case study of the Qilian Mountains Nature Reserve, China.

Unprecedented pulses of extreme precipitation due to climate change are causing significant stresses and impacts on regional and even global ecosystems. However, the relationship of vegetation response to this disturbance is unclear, such as phase characteristics, extent, timing, and degree. We summarize the nexus between vegetation resistance, recovery, and resilience under three stages of extreme precipitation pulses: duration, lagging, and post-disturbance, and then construct a pragmatic scheme to quantify and validate this complex relationship based on precipitation and Normalized Difference Vegetation Index (NDVI) data for the Qilian Mountains Nature Reserve (QMNR) from 2000 to 2020. The results show that the four extreme precipitation pulses were spring 2010 (118.98 mm), summer 2007 (312.25 mm), autumn 2010 (109.74 mm), and winter 2018 (6.84 mm). Extreme precipitations had a significant effect on vegetation in at least 98.5 % of the area, and there was also a two-month time lag effect. Specifically, the percentage of negative vegetation resistance in the face of four seasons of extreme precipitation pulses was 18.3 %, 2.0 %, 15.4 %, and 21.7 %, respectively, compared to negative recovery rates of 4.8 %, 11.9 %, 17.8 % and 10.2 % respectively, resilience was even more severe, with 20.1 %, 10.9 %, 16.1 % and 16.3 % of vegetation failing to rebound to normal levels within two months. The negative resistance, negative recovery, and weak resilience of vegetation under short-term extreme precipitation pulses are approximately 4.8, 3.7, and 5.3 times more fierce than long-term vegetation degradation. A total of 62 % of the four seasonal areas of severe negative resistance, severe negative recovery, and weak resilience were located in areas of moderate and significant steepness, which confirms that extreme precipitation pulses cause serious degradation of vegetation. Response of vegetation under extreme precipitation pulses is perceived, quantified, and validated in this study, which is essential for addressing climate change.

Nasal Caffeine Thermo-Sensitive In Situ Gel for Enhanced Cognition after Sleep-Deprivation.

BACKGROUND: Caffeine abundant in coffee has a strong excitation effect on the central nerve system (CNS). METHODS: To combat the adverse effects of sleep deprivation on physical and mental health, this article designed a new nasal temperature-sensitive gel loaded with caffeine, whose effects of awakening and improving cognition in sleep-deprived rats were evaluated. RESULTS: It was found that the caffeine thermo-sensitive in situ gel (TSG) stayed in the nasal cavity for a longer time and increased the contact time between the drugs and the nasal mucosa, which made it possible for caffeine TSG to exert a lasting effect. Secondly, compared with sleep-deprived rats, those administrated with caffeine TSG were more responsive in behavioral experiments. Moreover, the antipentobarbital test proved that caffeine TSG could prolong the sleep latency and shorten the sleep time. Furthermore, caffeine TSG could significantly restore the cognitive ability by ameliorating neuronal cell injuries by upregulating brain-derived neurotrophic factor (BDNF) levels. CONCLUSION: Generally, caffeine TSG could quickly exert the efficacy of enhancing cognition and wakefulness, and overcome the drawbacks of frequent medications. It can potentially be used for the treatment of psychiatric disorders, such as dementia, Parkinson and Alzheimer's disease.

Synthesis and evaluation of new carbonic anhydrase inhibitors.

A series of new sulfamide derivatives have been synthesized, their structures were confirmed by (1)H NMR and ESI-MS. Some target compounds were assessed by the tool of Dock6, and inhibition effects of all the new compounds on carbonic anhydrase II have been investigated. In addition, some compounds have been investigated for their antihypoxic effects in mice. Results indicated that nine target compounds exhibit as effectively as acetazolamide and 10 compounds have more potent inhibition effects on carbonic anhydrase II than acetazolamide. Three of them (I-8, I-18 and I'-3) can prolong markedly the survival time of mice in hypoxia, which are worth carrying out further studies.

A Photolabile Carboxyl Protecting Group for Solid Phase Peptide Synthesis.

A new kind of photolabile protecting group (PLPG) for carboxyl moieties was designed and synthesized as the linker between resin and peptide. This group can be used for the protection of amino acid carboxyl groups. The peptide was synthesized on Nph (2-hydroxy-3-(2-nitrophenyl)-heptanoic acid)-derivatized resins and could be cleaved under UV exposure, thus avoiding the necessity for harsh acid-mediated resin cleavage. The PLPG has been successfully used for solid-phase synthesis of peptides.

Synthesis and antitumor effects of novel benzyl naphthyl sulfoxide/sulfone derivatives derived from Rigosertib.

In this work, a series of novel benzyl naphthyl sulfoxides/sulfones derived from Rigosertib were designed and synthesized as potential antitumor agents. The in vitro cytotoxicity against four human cancer cell lines (HeLa, MCF-7, HepG2 and SCC-15) and two normal human cell lines (HUVEC and 293T) indicated that some of the sulfones and sulfoxides possessed potent antineoplastic activity that reached nanomolar levels and relatively low toxicity to normal cells. Among them, (2-methoxy-5-((naphthalen-2-ylsulfonyl)methyl)phenyl)glycine (15b) was found to be a promising antitumor drug candidate that could significantly inhibit tumor cell migration and induce tumor cell apoptosis via the p53-Bcl-2-Bax signaling pathway at nanomolar concentrations.

Application of armodafinil-loaded microneedle patches against the negative influence induced by sleep deprivation.

Cognition maintenance is essential for healthy and safe life if sleep deprivation happens. Armodafinil is a wake-promoting agent against sleep deprivation related disorders. However, only the tablet formulation is available, which may limit its potential in some circumstances. Here, we report the synthesis of a new formulation of armodafinil, microneedle patches, which can be conveniently used by any individual and removed in time if not wanted. To produce the needles of higher mechanical strength and higher drug loading, polyvinylpyrrolidone (PVP) K90 was used to fabricate armodafinil-loaded microneedles by applying the mold casting method after dissolving in methanol and drying. The higher mechanical strength was validated by COMSOL Multiphysics® software stimulation and universal mechanical testing machines. The obtained armodafinil microneedles can withstand a force of 70 N and penetrate the skin to a depth of 230 µm, and quickly released the drug within 1.5 h in vitro. The pharmacokinetic analysis showed that microneedle administration can maintain a more lasting and stable blood concentration as compared to oral administration. After the treatment of sleep deprived mice with microneedles, the in vivo pharmacodynamics study clearly demonstrated that armodafinil microneedles could eliminate the effects of sleep deprivation and improve the cognitive functions of sleep-deprived mice. A self-administered, high drug-loaded microneedle patch were prepared successfully, which appeared to be highly promising in preserving cognition by transdermal administration.

Preclinical Pharmacokinetics, Tissue Distribution, and Primary Safety Evaluation of Indo5, a Novel Selective Inhibitor of c-Met and Trks.

The compound [3-(1H-benzimidazol-2-methylene)-5-(2-methylphenylaminosulfo)-2-indolone], known as Indo5, is a novel selective inhibitor of c-Met and Trks, and it is a promising anticancer candidate against hepatocellular carcinoma (HCC). Assessing the pharmacokinetic properties, tissue distribution, and toxicity of Indo5 is critical for its medicinal evaluation. A series of sensitive and specific liquid chromatography-tandem mass spectrometry methods were developed and validated to determine the concentration of Indo5 in rat plasma and tissue homogenates. These methods were then applied to investigate the pharmacokinetics and tissue distribution of Indo5 in rats. After intravenous injection of Indo5, the maximum concentration (Cmax) and the time at which Cmax was reached (Tmax) were 1,565.3 ± 286.2 ng/ml and 1 min, respectively. After oral administration, Cmax and Tmax were 54.7 ± 10.4 ng/ml and 2.0 ± 0.48 h, respectively. We calculated the absolute oral bioavailability of Indo5 in rats to be 1.59%. Following intravenous injection, the concentrations of Indo5 in various tissues showed the following order: liver > kidney ≈ heart > lung ≈ large intestine ≈ small intestine ≈ stomach > spleen > brain ≈ testes; hence, Indo5 distributed highest in the liver and could not cross the blood-brain or blood-testes barriers. Continuous injection of Indo5 for 21 days did not lead to liver injury, considering unchanged ALT and AST levels, normal histological architecture of the liver, and normal number and frequencies of immune cells in the liver, indicating a very low toxicity of Indo5 in vivo. Collectively, our findings provide a comprehensive understanding of the biological actions of Indo5 in vivo and further support its development as an antitumor treatment for HCC patients.

Effects of armodafinil nanocrystal nasal hydrogel on recovery of cognitive function in sleep-deprived rats.

Armodafinil is typically used in clinical practice to maintain cognition and wakefulness in patients suffering from sleep deprivation. However, its poor water solubility and large dosage limit its effective application. Herein, we formulated armodafinil in a nanocrystal hydrogel (NCsG) with appropriate fluidity and viscosity, capable of rapidly dissolving after staying in the nasal cavity for > 4 h and then penetrating the mucosa as quickly as possible in vitro. We found that armodafinil NCsG was biologically safe, as it had no visible ciliary toxicity, as well as extremely stable due to the existence of intermolecular hydrogen-bonding forces. Nasal administration of armodafinil NCsG proved to be more efficient and targeted than oral administration due to its preferential absorption in plasma and more-concentrated distribution in the brain. In addition, compared with the model group, sleep-deprived rats treated with NCsG undergoing Morris water maze (MWM) behavioral experiments had shorter escape latency and much more shuttle times across the platform. Meanwhile, in the open-field test (OFT), these same rats had longer periods of movement in the center, longer time spent upright, and lower anxiety, which clearly demonstrated improved cognitive awareness and wakefulness after intranasal administration. Moreover, we speculated that armodafinil NCsG had a protective effect on hippocampal neurons in Cortical Area 1 (CA1), which is closely related to cognitive function, by upregulating brain-derived neurotrophic factor (BDNF) protein expression. Consequently, the intranasal administration of armodafinil NCsG could serve as a promising integrated-control measure for sleep deprivation.

Comparative study of oral and intranasal puerarin for prevention of brain injury induced by acute high-altitude hypoxia.

Human activities in the areas of high altitude have increased significantly recently. Brain is highly sensitive to changing of oxygen pressure due to high altitude, and this physiological response may lead to serious brain injury, such as learning and memory disabilities. Puerarin is a phytoestrogen with many pharmacological activities, such as treatment of neurological disorders. However, most of current drugs can not easily enter brain through the blood-brain barrier (BBB). The nose-to-brain route can bypass BBB for brain-targeting. Here, thermosensitive in situ hydrogels (TISGs) of puerarin were prepared with poloxamers 407, poloxamers 188 and propylene glycol to improve bioavailability and brain targeting. In vitro drug release in simulated nasal fluids, rheological properties and cilia toxicity of puerarin TISGs were explored. The pharmacodynamics and pharmacokinetics of puerarin by intranasal (i.n.) and oral (p.o.) administrations were also evaluated. The viscosity of puerarin TISGs tended to increase obviously with increased temperature. The puerarin release profile and transmucosal process of puerarin TISGs could be described with the first-order kinetics equation, depending on drug diffusion. The cilia toxicity of puerarin TISGs was not obvious. Rat models of hypobarism/hypoxia-induced brain injury were established with a hypobaric simulation chamber. Morris water maze and open filed tests indicated that puerarin TISGs improved the spatial memory and spontaneous exploratory behavior of the rats suffering from hypoxia-induced brain injury. Furthermore, puerarin TISGs decreased the level of oxidative stress cytokines (malondialdehyde (MDA) and glutathione (GSH)) in the peripheral circulation, alleviated the cerebral histological lesions, and relieved the expression of hypoxia-inducible factor-1α (HIF-1α). Intranasal puerarin TISGs were absorbed quickly with a shorter Tmax (10.0 ± 5.7 min) compared to that of oral puerarin (36 ± 13.4 min). In addition, the relative bioavailability of i.n. puerarin TISGs was high to 300% compared to oral administration of puerarin. The area under the curve (AUC) of brain after i.n. administration of puerarin TISGs was 954.5 ± 335.1 h.ng/mL, while no puerarin was detected in the brain after oral administration. Therefore, i.n. puerarin TISGs led to excellent brain targeting effect. Puerarin TISGs are an effective neuroprotector formulation for prevention of brain injury induced by acute high-altitude hypoxia.

Grubbs Catalysts Immobilized on Merrifield Resin for Metathesis of Leaf Alcohols by using a Convenient Recycling Approach.

Three new types of heterogeneous catalysts were prepared using a facile approach by the immobilization of Grubbs catalysts on PEGylated Merrifield resin. One of the immobilized catalysts was more efficient than the free catalyst for the metathesis of leaf alcohols in conversion and selectivity and was reused repeatedly (up to 5 cycles) with only a slight loss of activity (10.5 %). The long-chain PEGylated linker provided an appropriate distance between the resin and the catalytic center so that the ruthenium catalysts acted as the free catalyst.