Publications by authors named "Grigoriy Sereda"

16 Publications

  • Page 1 of 1

Targeting Colon Cancer Cells with Enzyme-Triggered Casein-Gated Release of Cargo from Mesoporous Silica-Based Nanoparticles.

Bioconjug Chem 2021 Oct 21. Epub 2021 Oct 21.

Department of Chemistry, The University of South Dakota, 414 E Clark Street, Vermillion, South Dakota 57069, United States.

Colorectal cancer (CRC) is one of the most widely diagnosed cancers worldwide. Despite notable improvements in therapeutic strategies available to CRC patients, late stages of CRC have a higher incidence rate of drug resistance, which is associated with a higher mortality rate. The development of therapeutic strategies that use nanoparticles as a drug delivery system has become one of the most promising potential approaches for cancer therapy. Previous studies have shown that a natural plant alkaloid, veratridine (VTD), suppresses colon cancer cell migration and invasion, two essential factors in tumor metastasis, through activation of the gene that encodes the tumor-suppressor protein UBXN2A. The goal of this study is to develop a nanoassembly to selectively deliver VTD to cancer cells and release it on demand while leaving normal cells intact. We packaged the targeted therapy anticancer molecule VTD inside mesoporous silica nanoparticles (MSNs) impermeable to the blood-brain barrier (BBB) and with selective affinity to CRC cells and sealed the VTD-loaded nanoparticles with an enzymatically cleavable protein. The particles will deliver and release VTD only at the targeted colorectal tumor sites. Since the enzyme MMP-7 protease is dominantly secreted by CRC cells, the release triggered by the enzymes will increase VTD concentration at tumor cells, enhancing the efficiency of the new therapy. We have proven the selective affinity of two types of VTD-carrying particles to CRC cells and enzyme- or acid-triggered VTD release. Negatively surface-charged MSNs showed significant affinity toward positively charged cancer cells but not negatively charged normal fibroblast colon cells, making VTD-MSNs a promising anticancer drug with minimal side effects.
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http://dx.doi.org/10.1021/acs.bioconjchem.1c00416DOI Listing
October 2021

QTL mapping of agronomic traits in wheat using the UK Avalon ×  Cadenza reference mapping population grown in Kazakhstan.

PeerJ 2021 18;9:e10733. Epub 2021 Feb 18.

Institute of Plant Biology and Biotechnology, Almaty, Kazakhstan.

Background: The success of wheat production is largely dependent on local breeding projects that focus on the development of high-yielding cultivars with the use of novel molecular tools. One strategy for improving wheat productivity involves the deployment of diverse germplasms with a high potential yield. An important factor for achieving success involves the dissection of quantitative trait loci (QTLs) for complex agronomic traits, such as grain yield components, in targeted environments for wheat growth.

Methods: In this study, we tested the United Kingdom (UK) spring set of the doubled haploid (DH) reference population derived from the cross between two British cultivars, Avalon (winter wheat) and Cadenza (spring wheat), in the Northern, Central, and Southern regions (Karabalyk, Karaganda, Kyzylorda) of Kazakhstan over three years (2013-2015). The DH population has previously been genotyped by UK scientists using 3647 polymorphic DNA markers. The list of tested traits includes the heading time, seed maturation time, plant height, spike length, productive tillering, number of kernels per spike, number of kernels per meter, thousand kernel weight, and yield per square meter. Windows QTL Cartographer was applied for QTL mapping using the composite interval mapping method.

Results: In total, 83 out of 232 QTLs were identified as stable QTLs from at least two environments. A literature survey suggests that 40 QTLs had previously been reported elsewhere, indicating that this study identified 43 QTLs that are presumably novel marker-trait associations (MTA) for these environments. Hence, the phenotyping of the DH population in new environments led to the discovery of novel MTAs. The identified SNP markers associated with agronomic traits in the DH population could be successfully used in local Kazakh breeding projects for the improvement of wheat productivity.
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http://dx.doi.org/10.7717/peerj.10733DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7897413PMC
February 2021

Synthesis, Characterization and Applications of Spinel Cobaltite Nanomaterials.

Curr Pharm Biotechnol 2021 ;22(6):773-792

Department of Chemistry, Guru Ghasidas Vishwavidyalaya (A Central University), Koni, Bilaspur - 495009 (Chhattisgarh), India.

Recently, spinel structures (ABO) Nanoparticles (NPs) having binary and ternary mixtures of metal oxides have been established as promising redox catalysts. Due to the presence of two mixed valence metal cations, transport of electrons takes place easily between multiple transition-metal cations with relatively low energy of activation. Among these, spinel cobaltite (MCoO) is very attractive due to its low cost, non-toxicity, higher stability, higher electronic conductivity and electrochemical property. To date, MCoO has been used in the fabrication of supercapacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. A variety of MMCoOmaterials have been synthesized, characterized, and utilized in the fabrication of super capacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. The progress in the field of the spinel MCoO materials opens the door to novel and efficient applications in the nanoscience and nanotechnology, and elctrochemistry.
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http://dx.doi.org/10.2174/1389201021666201117122002DOI Listing
June 2021

The tooth on-a-chip: a microphysiologic model system mimicking the biologic interface of the tooth with biomaterials.

Lab Chip 2020 01 19;20(2):405-413. Epub 2019 Dec 19.

Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR, USA. and Center for Regenerative Medicine, School of Medicine, Oregon Health & Science University, Portland, OR, USA and Department of Biomedical Engineering, School of Medicine, Oregon Health & Science University, Portland, OR, USA and Cancer Early Detection Advanced Research Center (CEDAR), Knight Cancer Institute, Portland, OR, USA.

The tooth has a unique configuration with respect to biomaterials that are used for its treatment. Cells inside of the dental pulp interface indirectly with biomaterials via a calcified permeable membrane, formed by the dentin matrix and several thousands of dentinal tubules (∼2 μm in diameter). Although the cytotoxic response of the dental pulp to biomaterials has been extensively studied, there is a shortage of in vitro model systems that mimic the dentin-pulp interface and enable an improved understanding of the morphologic, metabolic and functional influence of biomaterials on live dental pulp cells. To address this shortage, here we developed an organ-on-a-chip model system which integrates cells cultured directly on a dentin wall within a microfluidic device that replicates some of the architecture and dynamics of the dentin-pulp interface. The tooth-on-a-chip is made out of molded polydimethylsiloxane (PDMS) with a design consisting of two chambers separated by a dentin fragment. To characterize pulp cell responses to dental materials on-chip, stem cells from the apical papilla (SCAPs) were cultured in odontogenic medium and seeded onto the dentin surface, and observed using live-cell microscopy. Next, to evaluate the tooth-on-a-chip as a platform for materials testing, standard dental materials used clinically (2-hydroxyethylmethacrylate - HEMA, phosphoric acid - PA, and Adper-Scotchbond - SB) were tested for cytotoxicity, cell morphology, and metabolic activity on-chip, and compared against standardized off-chip controls. All dental materials had cytotoxic effects in both on-chip and off-chip systems in the following order: HEMA > SB > PA (p < 0.05), and cells presented consistently higher metabolic activity on-chip than off-chip (p < 0.05). Furthermore, the tooth-on-a-chip enabled real-time tracking of gelatinolytic activity in a model hybrid layer (HL) formed in the microdevice, which suggests that dental pulp cells may contribute to the proteolytic activity in the HL more than endogenous proteases. In conclusion, the tooth-on-a-chip is a novel platform that replicates near-physiologic conditions of the pulp-dentin interface and enables live-cell imaging to study dental pulp cell response to biomaterials.
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http://dx.doi.org/10.1039/c9lc00915aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7395925PMC
January 2020

Association mapping for agronomic traits in six-rowed spring barley from the USA harvested in Kazakhstan.

PLoS One 2019 12;14(8):e0221064. Epub 2019 Aug 12.

Institute of Plant Biology and Biotechnology, Almaty, Kazakhstan.

In barley, six-rowed barley is advantageous over two-rowed barley for feed due to the larger number of seeds per spike and the higher seed protein content. The growth of six-rowed barley is potentially important for breeding in agriculturally oriented countries, such as Kazakhstan. Nevertheless, until recently, very little attention was given to six-rowed barley in breeding projects in Kazakhstan, one of the largest countries in the world. In this study, phenotyping and single nucleotide polymorphism (SNP) genotyping data were generated from 275 accessions originating from six different breeding organizations in the USA as well as 9 accessions from Kazakhstan in field trials at six breeding institutions. The USA six-rowed barley was tested in comparison to local accessions over three years (2009-2011) based on analyses of key agronomic traits. It was determined that the average yield in the USA accessions in comparison to local lines showed heavier yield in all six tested sites. Principal Coordinate Analysis based on 1618 polymorphic SNP markers separated Kazakh lines from six USA barley origin groups based on PC1 (77.9%), and Montana lines from the remaining five USA groups based on PC2 (15.1%). A genome-wide association study based on eighteen field trials allowed the identification of 47 stable marker-trait associations (MTA) for ten agronomic traits, including key yield related characters such as yield per square meter, thousand grain weight, number of kernels per spike, and productive tillers. The comparison of chromosomal positions of identified MTA with positions of known genes and quantitative trait loci suggests that 25 out of those 47 MTAs are presumably novel. The analysis of 42 SNPs associated with 47 MTAs in the Ensemble genome annotation system (http://ensemblgenomes.org) suggested that 40 SNPs were in genic positions of the genome, as their sequences successfully aligned with corresponding Gen ID.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0221064PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6690582PMC
March 2020

Functionalized silk dental floss as a vehicle for delivery of bioactive minerals and ions to the tooth surface.

Am J Dent 2019 Jun;32(3):118-123

Department of Sustainability & Environment, University of South Dakota, Vermillion, South Dakota, USA.

Purpose: To enable the commercially available silk dental floss to carry a series of desensitizing, alkalizing, and tooth strengthening pharmacons.

Methods: The hydroxy-groups of the serine and tyrosine residues of the commercial silk dental floss were exposed by degumming, and employed as the chemical anchors for the introduction of carboxy-groups to the surface. The affinity of the silk dental floss to a set of bioactive species was studied by SEM, EDS, and XFS. The acetylated silk was used as a control sample for the experiments elucidating the effect of the surface carboxy-groups on its affinity to a series of pharmacons.

Results: While unmodified silk has affinity to microcrystals of sodium carbonate, some affinity to hydroxyapatite particles and Sr2+, its carboxylation drastically increased the affinity to hydroxyapatite, Sr2+, Ca2+ and K+. The unmodified silk had some affinity to existing hydroxyapatite particles, but did not initiate the growth of hydroxyapatite on the surface. Carboxylation of silk enabled the growth of hydroxyapatite on its surface, and significantly increased its affinity to the existing hydroxyapatite particles. The unmodified silk had significant affinity to Zn2+, which exceeded its acylated derivatives.

Clinical Significance: The ability of the commercial and modified silk floss to carry a series of pharmacons makes them precursors for a series of new versatile materials with a potential for delivering small doses of bioactive agents in a targeted manner.
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June 2019

Pre-treatment of dentin with chondroitin sulfate or L-arginine modulates dentin tubule occlusion by toothpaste components.

Am J Dent 2019 Apr;32(2):81-88

Department of Chemistry, University of South Dakota, Vermillion, South Dakota, USA.

Purpose: To evaluate the effect on dentin of chondroitin sulfate and L-arginine on dentin tubule occlusion.

Methods: The dentin samples were activated by submersion in an aqueous ( aq. ) solution of chondroitin sulfate ( ChS) or L-arginine prior to application of a commercial or custom-made toothpaste. After rinsing with water and ultrasonication, adhesion to dentin and occlusion of dentin tubules were evaluated by scanning electron microscopy and the elemental composition of the deposits was evaluated by energy-dispersive x-ray spectroscopy.

Results: Rinsing a dentin sample with a solution of ChS resulted in an increase in the adherence of dentifrices containing either titanium dioxide (TiO₂ ) or calcium-based nanoparticles [ hydroxyapatite ( HA\ or calcium carbonate( to the dentin surface. ChS does not appear to enhance the adherence of dentifrices lacking TiO₂. Pretreatment by L-arginine improved adherence of calcium carbonate nanoparticles, but less efficiently than ChS. Addition of nanoparticles of hydroxyapatite or calcium citrate to dentifrices improved their adherence to dentin without any pre-treatment.

Clinical Significance: The significant increase in adherence to the dentin surface of dentifrices of either TiO₂ or calcium-supplying nanoparticles to the dentin surface following pre-treatment with ChS or L-arginine opens the door to the development of two-step dental treatments, which accomplish dentin tubule occlusion and help to deliver active dentifrice components to the dentin surface. The ability of the aqueous pastes of nanoparticles of hydroxyapatite or calcium citrate to occlude dentin tubules enables the formulation of desensitizing dentifrices, which also supply the mineral and organic nutrients to the tooth surface.
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April 2019

Monitoring demineralization and remineralization of human dentin by characterization of its structure with resonance-enhanced AFM-IR chemical mapping, nanoindentation, and SEM.

Dent Mater 2019 04 23;35(4):617-626. Epub 2019 Feb 23.

University of Nebraska-Lincoln, 1400 R St., Lincoln, NE 68588, United States.

Objective: This research aimed at monitoring demineralization and remineralization of dentin and its collagen matrix at the nanoscale by amorphous, microcrystalline, and in situ formed hydroxyapatite.

Methods: The concurrent use of the resonance-enhanced atomic force microscopy coupled with infrared probe (AFM-IR) chemical mapping, nano-indentation, and scanning electron microscopy (SEM) provides a detailed insight into the structure of human dentin, as well as to the processes of its partial demineralization and remineralization.

Results: The resonance-enhanced AFM-IR chemical mapping of dentin has shown to be a useful method to follow distribution of its collagen and hydroxyapatite components at the micro- and nanoscale levels, especially in conjunction with SEM imaging and nanoindentation. Dentin with a higher extent of natural dentin tubule occlusion tends to be harder and less elastic. The relative affinity of the collagen and hydroxyapatite components of dentin toward hydroxyapatite depends on its type (amorphous, microcrystalline, or formed in-situ). The gel mineralization technique allows for an even and controlled growth of hydroxyapatite guided by the completely demineralized collagen matrix of dentin.

Significance: The observed trends of the affinity of collagen toward different forms of hydroxyapatite helps develop new remineralizing formulations. The employed methods of characterization may provide an insight to the natural processes of bone mineralization guided by its both hydroxyapatite and protein constituents.
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http://dx.doi.org/10.1016/j.dental.2019.02.007DOI Listing
April 2019

Marker-trait associations in two-rowed spring barley accessions from Kazakhstan and the USA.

PLoS One 2018 11;13(10):e0205421. Epub 2018 Oct 11.

Institute of Plant Biology and Biotechnology, Almaty, Kazakhstan.

In this study, phenotyping and single nucleotide polymorphism (SNP) genotyping data of 272 accessions of two-rowed spring barley from the USA along with 94 accessions from Kazakhstan were assessed in field trials at six breeding organizations in Kazakhstan to evaluate the performance of the USA samples over three years (2009-2011). The average grain yield over the six locations was not significantly higher in Kazakh accessions in comparison to the USA samples. Twenty four samples from Montana, Washington, the USDA station in Aberdeen Idaho, and the Anheuser-Busch breeding programs showed heavier average yield than the local standard cultivar "Ubagan". Principal Coordinate analysis based on two sets of SNP data suggested that Kazakh accessions were closest to the USA accessions among eight groups of samples from different parts of the World, and within five US barley origin groups the samples from Montana and Washington perfectly matched six groups of Kazakh breeding origins. A genome-wide association study (GWAS) using data from eighteen field trials allowed the identification of ninety one marker-trait associations (MTA) in two or more environments for nine traits, including key characters such as heading time (HT), number of kernels per spike (NKS), and thousand grain weight (TGW). Our GWAS allowed the identification of eight MTA for HT and NKS, and sixteen MTA for TGW, when those MTA were linked to mapped SNPs. Based on comparisons of chromosomal positions of MTA identified in this study, and positions of known genes and quantitative trait loci for HT, NKS and TGW, it was suggested that MTA for HT on chromosome 2H (at 158.2 cM, 11_21414), MTA for NKS on 5H (at 118.6 cM, 11_20298), and two MTA for TGW on chromosome 4H (at 94.7 cM, 12_30718, and at 129.3 cM, 11_20013) were potentially new associations in barley. GWAS suggested that six MTA for HT, including two on chromosome 1H, two on chromosome 3H, and one each on chromosomes 4H and 6H, had useful pleiotropic effects for improving barley spike traits.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0205421PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181366PMC
March 2019

GWAS for plant growth stages and yield components in spring wheat (Triticum aestivum L.) harvested in three regions of Kazakhstan.

BMC Plant Biol 2017 Nov 14;17(Suppl 1):190. Epub 2017 Nov 14.

Institute of Plant Biology and Biotechnology, Almaty, Kazakhstan, 050040.

Background: Spring wheat is the largest agricultural crop grown in Kazakhstan with an annual sowing area of 12 million hectares in 2016. Annually, the country harvests around 15 million tons of high quality grain. Despite environmental stress factors it is predicted that the use of new technologies may lead to increases in productivity from current levels of 1.5 to up to 3 tons per hectare. One way of improving wheat productivity is by the application of new genomic oriented approaches in plant breeding projects. Genome wide association studies (GWAS) are emerging as powerful tools for the understanding of the inheritance of complex traits via utilization of high throughput genotyping technologies and phenotypic assessments of plant collections. In this study, phenotyping and genotyping data on 194 spring wheat accessions from Kazakhstan, Russia, Europe, and CIMMYT were assessed for the identification of marker-trait associations (MTA) of agronomic traits by using GWAS.

Results: Field trials in Northern, Central and Southern regions of Kazakhstan using 194 spring wheat accessions revealed strong correlations of yield with booting date, plant height, biomass, number of spikes per plant, and number of kernels per spike. The accessions from Europe and CIMMYT showed high breeding potential for Southern and Central regions of the country in comparison with the performance of the local varieties. The GGE biplot method, using average yield per plant, suggested a clear separation of accessions into their three breeding origins in relationship to the three environments in which they were evaluated. The genetic variation in the three groups of accessions was further studied using 3245 polymorphic SNP (single nucleotide polymorphism) markers. The application of Principal Coordinate analysis clearly grouped the 194 accessions into three clades according to their breeding origins. GWAS on data from nine field trials allowed the identification of 114 MTAs for 12 different agronomic traits.

Conclusions: Field evaluation of foreign germplasm revealed its poor yield performance in Northern Kazakhstan, which is the main wheat growing region in the country. However, it was found that EU and CIMMYT germplasm has high breeding potential to improve yield performance in Central and Southern regions. The use of Principal Coordinate analysis clearly separated the panel into three distinct groups according to their breeding origin. GWAS based on use of the TASSEL 5.0 package allowed the identification of 114 MTAs for twelve agronomic traits. The study identifies a network of key genes for improvement of yield productivity in wheat growing regions of Kazakhstan.
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http://dx.doi.org/10.1186/s12870-017-1131-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5688510PMC
November 2017

Expression Level of the -Type Gene, Identified with Amplifluor SNP Markers, Correlates with Performance, and Tolerance to Dehydration in Bread Wheat Cultivars from Northern Kazakhstan.

Front Plant Sci 2016 18;7:1736. Epub 2016 Nov 18.

School of Agriculture, Food and Wine, Faculty of Sciences, University of Adelaide Urrbrae, SA, Australia.

A panel of 89 local commercial cultivars of bread wheat was tested in field trials in the dry conditions of Northern Kazakhstan. Two distinct groups of cultivars (six cultivars in each group), which had the highest and the lowest grain yield under drought were selected for further experiments. A dehydration test conducted on detached leaves indicated a strong association between rates of water loss in plants from the first group with highest grain yield production in the dry environment relative to the second group. Modern high-throughput Amplifluor Single Nucleotide Polymorphism (SNP) technology was applied to study allelic variations in a series of drought-responsive genes using 19 SNP markers. Genotyping of an SNP in the (-type) gene using the Amplifluor SNP marker KATU48 revealed clear allele distribution across the entire panel of wheat accessions, and distinguished between the two groups of cultivars with high and low yield under drought. Significant differences in expression levels of were revealed by qRT-PCR. Most wheat plants from the first group of cultivars with high grain yield showed slight up-regulation in the TaDREB5 transcript in dehydrated leaves. In contrast, expression of in plants from the second group of cultivars with low grain yield was significantly down-regulated. It was found that SNPs did not alter the amino acid sequence of TaDREB5 protein. Thus, a possible explanation is that alternative splicing and up-stream regulation of may be affected by SNP, but these hypotheses require additional analysis (and will be the focus of future studies).
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http://dx.doi.org/10.3389/fpls.2016.01736DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114286PMC
November 2016

Vaccination against the M protein of Streptococcus pyogenes prevents death after influenza virus: S. pyogenes super-infection.

Vaccine 2014 Sep 29;32(40):5241-9. Epub 2014 Jul 29.

Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, United States. Electronic address:

Influenza virus infections are associated with a significant number of illnesses and deaths on an annual basis. Many of the deaths are due to complications from secondary bacterial invaders, including Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pyogenes. The β-hemolytic bacteria S. pyogenes colonizes both skin and respiratory surfaces, and frequently presents clinically as strep throat or impetigo. However, when these bacteria gain access to normally sterile sites, they can cause deadly diseases including sepsis, necrotizing fasciitis, and pneumonia. We previously developed a model of influenza virus:S. pyogenes super-infection, which we used to demonstrate that vaccination against influenza virus can limit deaths associated with a secondary bacterial infection, but this protection was not complete. In the current study, we evaluated the efficacy of a vaccine that targets the M protein of S. pyogenes to determine whether immunity toward the bacteria alone would allow the host to survive an influenza virus:S. pyogenes super-infection. Our data demonstrate that vaccination against the M protein induces IgG antibodies, in particular those of the IgG1 and IgG2a isotypes, and that these antibodies can interact with macrophages. Ultimately, this vaccine-induced immunity eliminated death within our influenza virus:S. pyogenes super-infection model, despite the fact that all M protein-vaccinated mice showed signs of illness following influenza virus inoculation. These findings identify immunity against bacteria as an important component of protection against influenza virus:bacteria super-infection.
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http://dx.doi.org/10.1016/j.vaccine.2014.06.093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4146501PMC
September 2014

Pd-MCM-48: a novel recyclable heterogeneous catalyst for chemo- and regioselective hydrogenation of olefins and coupling reactions.

Org Biomol Chem 2010 Oct 29;8(19):4316-21. Epub 2010 Jul 29.

Department of Chemistry, The University of South Dakota, Vermillion, SD 57069, USA.

A novel, heterogeneous Pd-MCM-48 catalyst has been developed by encapsulating palladium nanoparticles into the cubic phase of mesoporous MCM-48 matrix at room temperature. The catalyst demonstrated excellent chemo- and regioselectivity for the hydrogenation of olefins at room temperature within 30-80 min. The turnover frequency for the hydrogenation is very high (4400 h(-1)). Interestingly, selectivity of the catalyst was significantly influenced by the mode of addition of palladium precursor. Moreover, the catalyst was also very effective for the coupling reactions with the formation of carbon-carbon and carbon-nitrogen bonds under ligand-free and aerobic conditions.
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http://dx.doi.org/10.1039/c0ob00183jDOI Listing
October 2010

Effect of transannular interaction on the redox-potentials in a series of bicyclic quinones.

Beilstein J Org Chem 2006 Dec 8;2:26. Epub 2006 Dec 8.

The University of South Dakota, Department of Chemistry 414 E, Clark St,, Vermillion, SD 57069, USA.

Background: Better understanding of the transannular influence of a substituent on the redox-potentials of bicyclo[2.2.2]octane-derived quinones will help in the design of new compounds with controlled biological activity. However, attempts to directly relate the reduction potentials of substituted triptycene-quinones to the electronic effects of substituents are often unsuccessful.

Results: First and second redox-potentials of a series of bicyclic quinones are compared to computed energies of their LUMO, LUMO+1, and energies of reduction. Transannular influence of substituent on the redox-potentials is rationalized in terms of MO theory. Acetoxy-substituents in the 5,8-positions of the triptycene-quinone system selectively destabilize the product of the two-electron reduction.

Conclusion: We have shown that first redox-potentials of substituted bicyclic quinones correlate with their calculated LUMO energies and the energies of reduction. The second redox-potentials correlate with calculated LUMO+1 energies. As opposed to the LUMO orbitals, the LUMO+1 orbital coefficients are weighted significantly on the non-quinone part of the bicyclic system. This accounts for: (1) significantly larger substituent effect on the second redox-potentials, than on the first redox-potentials; (2) lack of stability of the product of two electron reduction of 5,8-diacetoxy-9,10-dihydro-9,10-[1,2]benzenoanthracene-1,4-dione 5.
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http://dx.doi.org/10.1186/1860-5397-2-26DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1779790PMC
December 2006

Solution and crystal lattice effects on the photochemistry of 6-substituted cyclohexenones(1)(,)(2).

J Org Chem 2003 Jan;68(2):283-92

Chemistry Department, University of Wisconsin, Madison, 53706, USA.

The photochemistry of 13 4,4-diphenylcyclohexenones, substituted at carbon-6, was investigated in solution and in the crystalline state. The stereoselectivity was of particular interest. In the solution photochemistry of C-6 monosubstituted enones in benzene, there was a unique preference for migration of the cis-phenyl group with formation of bicyclo[3.1.0]hexanone photoproducts, with the original 6-substituent having an endo configuration at carbon-3 of the product. In methanol the reaction was diverted to afford 3,4-diphenylcyclohex-2-enes understood as arising from a hydrogen-bonded zwitterionic intermediate. The solid-state photochemistry was also investigated. There was a dramatic absence of the 3,4-diphenylcyclohex-2-ene products in accord with the absence of the hydrogen bonding encountered in methanol. Further, the solid-state reactivity correlated with a vector analysis using X-ray atomic coordinates. This established that the migrating phenyl group required an orientation facing the enone beta-carbon. While the interesting preference for the cis-endo migration was not intuitively predicted, ab initio computations on the alternative phenyl-bridged triplet intermediates did lead to an understanding of the selectivity.
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http://dx.doi.org/10.1021/jo026279eDOI Listing
January 2003
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