Heme and Nonheme High-Valent Iron and Manganese Oxo Cores in Biological and Abiological Oxidation Reactions

Guo, Mian,Corona, Teresa,Ray, Kallol,Nam, Wonwoo American Chemical Society 2019 ACS central science Vol.5 No.1

<▼1><P/><P>Utilization of O<SUB>2</SUB> as an abundant and environmentally benign oxidant is of great interest in the design of bioinspired synthetic catalytic oxidation systems. Metalloenzymes activate O<SUB>2</SUB> by employing earth-abundant metals and exhibit diverse reactivities in oxidation reactions, including epoxidation of olefins, functionalization of alkane C–H bonds, arene hydroxylation, and <I>syn</I>-dihydroxylation of arenes. Metal–oxo species are proposed as reactive intermediates in these reactions. A number of biomimetic metal–oxo complexes have been synthesized in recent years by activating O<SUB>2</SUB> or using artificial oxidants at iron and manganese centers supported on heme or nonheme-type ligand environments. Detailed reactivity studies together with spectroscopy and theory have helped us understand how the reactivities of these metal–oxygen intermediates are controlled by the electronic and steric properties of the metal centers. These studies have provided important insights into biological reactions, which have contributed to the design of biologically inspired oxidation catalysts containing earth-abundant metals like iron and manganese. In this Outlook article, we survey a few examples of these advances with particular emphasis in each case on the interplay of catalyst design and our understanding of metalloenzyme structure and function.</P></▼1><▼2><P>This Outlook summarizes the recent advances in bioinspired oxidation catalysis with particular emphasis on the interplay of catalyst design and knowledge of metalloenzyme structure and function.</P></▼2>

Provisioning of QoS Adaptability in Wired-Wireless Integrated Networks

Guo, Mian,Jiang, Shengming,Guan, Quansheng,Mao, Huachao The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.1

The increasing number of mobile users and the popularity of real-time applications make wired-wireless integrated network extremely attractive. In this case, quality of service (QoS) adaptability is particularly important since some important features of the integrated network call for QoS adaptability, such as mobility, bursty applications and so on. Traditional QoS schemes include integrated service (IntServ) and differentiated service (DiffSev) as well as their variants. However, they are not able to balance well between scalability and QoS granularity. For example, IntServ faces the scalability problem, while DiffServ can only provide coarse granular QoS. In addition, they are also unable to efficiently support QoS adaptability. Therefore, a per-packet differentiated queueing service (DQS) was proposed. DQS was originally proposed to balance between scalability and QoS granularity in wired networks and then extended to wireless networks. This paper mainly discusses how to use DQS to support QoS adaptability in wired-wireless integrated networks. To this end, we propose a scheme to determine dynamic delay bounds, which is the key step to implement DQS to support QoS adaptability. Simulation studies along with some discussions are further conducted to investigate the QoS adaptability of the proposed scheme, especially in terms of its support of QoS adaptability to mobility and to bursty real-time applications.

Highly Reactive Manganese(IV)-Oxo Porphyrins Showing Temperature-Dependent Reversed Electronic Effect in C-H Bond Activation Reactions

Guo, Mian,Seo, Mi Sook,Lee, Yong-Min,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.31

<P>We report that Mn(IV)-oxo porphyrin complexes, Mn<SUP>IV</SUP>(O)(TMP) (<B>1</B>) and Mn<SUP>IV</SUP>(O)(TDCPP) (<B>2</B>), are capable of activating the C-H bonds of hydrocarbons, including unactivated alkanes such as cyclohexane, via an oxygen non-rebound mechanism. Interestingly, <B>1</B> with an electron-rich porphyrin is more reactive than <B>2</B> with an electron-deficient porphyrin at a high temperature (e.g., 0 °C). However, at a low temperature (e.g., −40 °C), the reactivity of <B>1</B> and <B>2</B> is reversed, showing that <B>2</B> is more reactive than <B>1</B>. To the best of our knowledge, the present study reports the first example of highly reactive Mn(IV)-oxo porphyrins and their temperature-dependent reactivity in C-H bond activation reactions.</P> [FIG OMISSION]</BR>

Provisioning of QoS Adaptability in Wired-Wireless Integrated Networks

Mian Guo,Shengming Jiang,Quansheng Guan,Huachao Mao 한국통신학회 2013 Journal of communications and networks Vol.15 No.1

The increasing number of mobile users and the popularity of real-time applications make wired-wireless integrated network extremely attractive. In this case, quality of service (QoS)adaptability is particularly important since some important features of the integrated network call for QoS adaptability, such as mobility, bursty applications and so on. Traditional QoS schemes include integrated service (IntServ) and differentiated service (DiffSev) as well as their variants. However, they are not able to balance well between scalability and QoS granularity. For example,IntServ faces the scalability problem, while DiffServ can only provide coarse granular QoS. In addition, they are also unable to efficiently support QoS adaptability. Therefore, a per-packet differentiated queueing service (DQS) was proposed. DQS was originally proposed to balance between scalability and QoS granularity in wired networks and then extended to wireless networks. This paper mainly discusses how to use DQS to support QoS adaptability in wired-wireless integrated networks. To this end, we propose a scheme to determine dynamic delay bounds, which is the key step to implement DQS to support QoS adaptability. Simulation studies along with some discussions are further conducted to investigate the QoS adaptability of the proposed scheme, especially in terms of its support of QoS adaptability to mobility and to bursty real-time applications.

Mn(III)-Iodosylarene Porphyrins as an Active Oxidant in Oxidation Reactions: Synthesis, Characterization, and Reactivity Studies

Guo, Mian,Lee, Yong-Min,Seo, Mi Sook,Kwon, Yong-Ju,Li, Xiao-Xi,Ohta, Takehiro,Kim, Won-Suk,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2018 Inorganic Chemistry Vol.57 No.16

<P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at −60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)]<SUP>+</SUP> species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. For example, cyclohexene oxide was formed exclusively with trace amounts of allylic oxidation products; <I>cis</I>- and <I>trans</I>-stilbenes were oxidized to the corresponding <I>cis</I>- and <I>trans</I>-stilbene oxides, respectively. In the catalytic epoxidation of cyclohexene by an electron-deficient Mn(III) porphyrin complex and <SUP>s</SUP>PhIO at low temperature (e.g., −60 °C), the Mn(III)-iodosylarene porphyrin species was evidenced as the active oxidant that effects the olefin epoxidation to give epoxide as the product. However, at high temperature (e.g., 0 °C) or in the case of using an electron-rich manganese(III) porphyrin catalyst, allylic oxidation products, along with cyclohexene oxide, were yielded, indicating that the active oxidant(s) was not the Mn(III)-iodosylarene adduct but probably high-valent Mn-oxo species in the catalytic reactions. We also report the conversion of the Mn(III)-iodosylarene porphyrins to high-valent Mn-oxo porphyrins under various conditions, such as at high temperature, with electron-rich porphyrin ligand, and in the presence of base (OH<SUP>-</SUP>). The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions. Other aspects, such as one oxidant versus multiple oxidants debate, also were discussed.</P><P>Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]<SUP>+</SUP>, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) and characterized using various spectroscopic methods. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions.</P> [FIG OMISSION]</BR>

Dioxygen Activation and O-O Bond Formation Reactions by Manganese Corroles

Guo, Mian,Lee, Yong-Min,Gupta, Ranjana,Seo, Mi Sook,Ohta, Takehiro,Wang, Hua-Hua,Liu, Hai-Yang,Dhuri, Sunder N.,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.44

<P>Activation of dioxygen (O-2) in enzymatic and biomimetic reactions has been intensively investigated over the past several decades. More recently, O-O bond formation, which is the reverse of the O-2-activation reaction, has been the focus of current research. Herein, we report the O-2-activation and O-O bond formation reactions by manganese corrole complexes. In the O-2-activation reaction, Mn(V)-oxo and Mn(IV)-peroxo intermediates were formed when Mn(III) corroles were exposed to O-2 in the presence of base (e.g., OH-) and hydrogen atom (H atom) donor (e.g., THE or cyclic olefins); the O-2-activation reaction did not occur in the absence of base and H atom donor. Moreover, formation of the Mn(V)-oxo and Mn(IV)-peroxo species was dependent on the amounts of base present in the reaction solution. The role of the base was proposed to lower the oxidation potential of the Mn(III) corroles, thereby facilitating the binding of O-2 and forming a Mn(IV)-superoxo species. The putative Mn(IV)-superoxo species was then converted to the corresponding Mn(IV)-hydroperoxo species by abstracting a H atom from H atom donor, followed by the O-O bond cleavage of the putative Mn(IV)-hydroperoxo species to form a Mn(V)-oxo species. We have also shown that addition of hydroxide ion to the Mn(V)-oxo species afforded the Mn(IV)-peroxo species via O-O bond formation and the resulting Mn(IV)-peroxo species reverted to the Mn(V)-oxo species upon addition of proton, indicating that the O-O bond formation and cleavage reactions between the Mn(V)-oxo and Mn(IV)-peroxo complexes are reversible. The present study reports the first example of using the same manganese complex in both O-2-activation and O-O bond formation reactions.</P>

Influence of Peanut Cultivars and Environmental Conditions on the Diversity and Community Composition of Pod Rot Soil Fungi in China

( Mian Wang ),( Mingna Chen ),( Zhen Yang ),( Na Chen ),( Xiaoyuan Chi ),( Lijuan Pan ),( Tong Wang ),( Shanlin Yu ),( Xingqi Guo ) 한국균학회 2017 Mycobiology Vol.45 No.4

Peanut yield and quality are seriously affected by pod rot pathogens worldwide, especially in China in recent years. The goals of this study are to analyze the structure of fungal communities of peanut pod rot in soil in three peanut cultivars and the correlation of pod rot with environmental variables using 454 pyrosequencing. A total of 46,723 internal transcribed spacer high-quality sequences were obtained and grouped into 1,706 operational taxonomic units at the 97% similarity cut-off level. The coverage, rank abundance, and the Chao 1 and Shannon diversity indices of the operational taxonomic units were analyzed. Members of the phylum Ascomycota were dominant, such as Fusarium, Chaetomium, Alternaria, and Sordariomycetes, followed by Basidiomycota. The results of the heatmap and redundancy analysis revealed significant variation in the composition of the fungal community among the three cultivar samples. The environmental conditions in different peanut cultivars may also influence on the structure of the fungal community. The results of this study suggest that the causal agent of peanut pod rot may be more complex, and cultivars and environmental conditions are both important contributors to the community structure of peanut pod rot fungi.

Influence of Peanut Cultivars and Environmental Conditions on the Diversity and Community Composition of Pod Rot Soil Fungi in China

Wang, Mian,Chen, Mingna,Yang, Zhen,Chen, Na,Chi, Xiaoyuan,Pan, Lijuan,Wang, Tong,Yu, Shanlin,Guo, Xingqi The Korean Society of Mycology 2017 Mycobiology Vol.45 No.4

Peanut yield and quality are seriously affected by pod rot pathogens worldwide, especially in China in recent years. The goals of this study are to analyze the structure of fungal communities of peanut pod rot in soil in three peanut cultivars and the correlation of pod rot with environmental variables using 454 pyrosequencing. A total of 46,723 internal transcribed spacer high-quality sequences were obtained and grouped into 1,706 operational taxonomic units at the 97% similarity cut-off level. The coverage, rank abundance, and the Chao 1 and Shannon diversity indices of the operational taxonomic units were analyzed. Members of the phylum Ascomycota were dominant, such as Fusarium, Chaetomium, Alternaria, and Sordariomycetes, followed by Basidiomycota. The results of the heatmap and redundancy analysis revealed significant variation in the composition of the fungal community among the three cultivar samples. The environmental conditions in different peanut cultivars may also influence on the structure of the fungal community. The results of this study suggest that the causal agent of peanut pod rot may be more complex, and cultivars and environmental conditions are both important contributors to the community structure of peanut pod rot fungi.

TWO COMPARISON THEOREMS OF BSDES

Huang, Xiao-Qin,Wang, Mian-Sen,Jia, Jun-Guo 한국전산응용수학회 2007 Journal of applied mathematics & informatics Vol.24 No.1

In this paper, by the equations of Mao [9] and Peng [5], we use the martingale method to establish the comparison theorems of backward stochastic differential equations (BSDEs). We generalize the results of Cao-Yan [1].

High-Spin Mn(V)-Oxo Intermediate in Nonheme Manganese Complex-Catalyzed Alkane Hydroxylation Reaction: Experimental and Theoretical Approach

Li, Xiao-Xi,Guo, Mian,Qiu, Bin,Cho, Kyung-Bin,Sun, Wei,Nam, Wonwoo American Chemical Society 2019 Inorganic Chemistry Vol.58 No.21

<P>Mononuclear nonheme manganese complexes are highly efficient catalysts in the catalytic oxidation of hydrocarbons by hydrogen peroxide in the presence of carboxylic acids. Although high-valent Mn(V)-oxo complexes have been proposed as the active oxidants that afford high regio-, stereo-, and enantioselectivities in the catalytic oxidation reactions, the importance of the spin state (e.g., <I>S</I> = 0 or 1) of the proposed Mn(V)-oxo species is an area that requires further study. In the present study, we have theoretically demonstrated that a mononuclear nonheme Mn(V)-oxo species with an <I>S</I> = 1 ground spin state is the active oxidant that effects the stereo- and enantioselective alkane hydroxylation reaction; it is noted that synthetic octahedral Mn(V)-oxo complexes, characterized spectroscopically and/or structurally, possess an <I>S</I> = 0 spin state and are sluggish oxidants. In an experimental approach, we have investigated the catalytic hydroxylation of alkanes by a mononuclear nonheme Mn(II) complex, [(<I>S</I>-PMB)Mn<SUP>II</SUP>]<SUP>2+</SUP>, and H<SUB>2</SUB>O<SUB>2</SUB> in the presence of carboxylic acids; alcohol is the major product with high stereo- and enantioselectivities. A synthetic Mn(IV)-oxo complex, [(<I>S</I>-PMB)Mn<SUP>IV</SUP>(O)]<SUP>2+</SUP>, is inactive in C-H bond activation reactions, ruling out the Mn(IV)-oxo species as an active oxidant. DFT calculations have shown that a Mn(V)-oxo species with an <I>S</I> = 1 spin state, [(<I>S</I>-PMB)Mn<SUP>V</SUP>(O)(OAc)]<SUP>2+</SUP>, is highly reactive and capable of oxygenating the C-H bond via oxygen rebound mechanism; we propose that the triplet spin state of the Mn(V)-oxo species results from the consequence of breaking the equatorial symmetry due to the binding of an equatorial oxygen from an acetate ligand. Thus, the present study reports that, different from the previously reported <I>S</I> = 0 Mn(V)-oxo species, Mn(V)-oxo species with a triplet ground spin state are highly reactive oxidants that are responsible for the regio-, stereo-, and enantioselectivities in the catalytic hydroxylation of alkanes by mononuclear nonheme manganese complexes and terminal oxidants.</P><P>It is theoretically demonstrated that a mononuclear nonheme Mn(V)-oxo species with an <I>S</I> = 1 ground spin state, [(<I>S</I>-PMB)Mn<SUP>V</SUP>(O)(OAc)]<SUP>2+</SUP>, is highly reactive and capable of oxygenating the C−H bond via oxygen rebound mechanism. Thus, it is proposed that a triplet spin state (<I>S</I> = 1) Mn(V)-oxo intermediate is generated as an active oxidant that is responsible for the regio-, stereo-, and enantioselectivities in the catalytic hydroxylation of alkanes by nonheme manganese catalysts and terminal oxidants.</P> [FIG OMISSION]</BR>