Tripodal, Cooperative, and Allosteric Transphosphorylation Metallocatalysts

Self Cite

The catalytic activity of a series of Au monolayer protected colloids (Au MPCs) containing different ratios of the catalytic unit triazacyclononane⋅Zn(II) (TACN⋅Zn(II) ) and an inert triethyleneglycol (TEG) unit was measured. The catalytic self-assembled monolayers (SAMs) are highly efficient in the transphosphorylation of 2-hydroxy propyl 4-nitrophenyl phosphate (HPNPP), an RNA model substrate, exhibiting maximum values for the Michaelis-Menten parameters k(cat) and K(M) of 6.7×10(-3) s(-1) and 3.1×10(-4) M, respectively, normalized per catalytic unit. Despite the structural simplicity of the catalytic units, this renders these nanoparticles among the most active catalysts known for this substrate. Both k(cat) and K(M) parameters were determined as a function of the mole fraction of catalytic unit (x(1)) in the SAM. Within this nanoparticle (NP) series, k(cat) increases up till x(1) ≈0.4, after which it remains constant and K(M) decreases exponentially over the range studied. A theoretical analysis demonstrated that these trends are an intrinsic property of catalytic SAMs, in which catalysis originates from the cooperative effect between two neighboring catalytic units. The multivalency of the system causes an increase of the number of potential dimeric catalytic sites composed of two catalytic units as a function of the x(1) , which causes an apparent increase in binding affinity (decrease in K(M)). Simultaneously, the k(cat) value is determined by the number of substrate molecules bound at saturation. For values of x(1) >0.4, isolated catalytic units are no longer present and all catalytic units are involved in catalysis at saturation. Importantly, the observed trends are indicative of a random distribution of the thiols in the SAM. As indicated by the theoretical analysis, and confirmed by a control experiment, in case of clustering both k(cat) and K(M) values remain constant over the entire range of x(1) .

Section: Resultsmentioning

confidence: 99%

Catalytic Self‐Assembled Monolayers on Au Nanoparticles: The Source of Catalysis of a Transphosphorylation Reaction

Zaupa¹,

Mora²,

Bonomi³

et al. 2011

Self Cite

“…Nanoparticle concentration is expressed as ac oncentration of the TACN head groups on the surface of the gold nanoparticles. [34] Determination of surface saturationconcentration (SSC)…”

Section: Experimental Protocolsmentioning

confidence: 99%

Temporal Control over Transient Chemical Systems using Structurally Diverse Chemical Fuels

Chen

Maiti

Fortunati

et al. 2017

Self Cite

The next generation of adaptive, intelligent chemical systems will rely on a continuous supply of energy to maintain the functional state. Such systems will require chemical methodology that provides precise control over the energy dissipation process, and thus, the lifetime of the transiently activated function. This manuscript reports on the use of structurally diverse chemical fuels to control the lifetime of two different systems under dissipative conditions: transient signal generation and the transient formation of self-assembled aggregates. The energy stored in the fuels is dissipated at different rates by an enzyme, which installs a dependence of the lifetime of the active system on the chemical structure of the fuel. In the case of transient signal generation, it is shown that different chemical fuels can be used to generate a vast range of signal profiles, allowing temporal control over two orders of magnitude. Regarding self-assembly under dissipative conditions, the ability to control the lifetime using different fuels turns out to be particularly important as stable aggregates are formed only at well-defined surfactant/fuel ratios, meaning that temporal control cannot be achieved by simply changing the fuel concentration.

“…[190] Five years later he was able to follow up on this by reporting on a modified catalyst 153 (Scheme 97) whose transphosphorylation activity could also be controlled by zinc(II) ins in a positively cooperative manner. [191] Another class of oligodentate ligands with multiple metal binding sites was developed by Shinkai. The activity of his catalyst 154 in H 2 O/EtOH (2:1) was also found to depend on the presence of zinc(II) ions acting as a positive allosteric effector (Scheme 98).…”

Section: Allosteric Control Of Reactivitymentioning

confidence: 99%

Artificial Allosteric Receptors

Kremer¹,

Lützen²

2013

131

Cooperative effects in the binding of two or more substrates to different binding sites of a receptor that are a result of a conformational change caused by the binding of the first substrate--also referred to as the effector--are called allosteric effects. In biological systems, allosteric regulation is a widely used mechanism to control the function of proteins and enzymes in cellular metabolism. Inspired by this a lot of efforts have been made in supramolecular chemistry to implement this concept into artificial systems to control functions as molecular recognition, signal amplification, or even reactivity and catalysis. This review gives an up-to-date overview over the different approaches that have been reported ever since the first examples from the late 1970s/early 1980s. It covers both homo- and heterotropic examples and is divided according to the nature of the effector--cationic, anionic, or neutral--effectors and systems that use combinations of those.