Physicochemical probes

The example above of tire stopped-flow apparatus demonstrates some of tire requirements important for all fonns of transient spectroscopy. These are tire ability to provide a perturbation (pump) to tire physicochemical system under study on a time scale tliat is as fast or faster tlian tire time evolution of tire process to be studied, the ability to synclironize application of tire pump and tire probe on tliis time scale and tire ability of tire detection system to time resolve tire changes of interest. 

Table 7.4 summarizes the key pharmacokinetic (PK) and physicochemical properties of the selected probe molecules, consisting of bases, acids, and neutral species. 

Metal nanoparticles have been actively synthesized for applications as catalysts, sensors, adsorbents, analytical probes and optical data storages [1-7]. This is due to the fact that the physicochemical properties of metal nanoparticles can be... 

It is necessary to note that fluorescence characteristics demonstrate remarkable sensitivity to variations of physicochemical parameters of the environment. Therefore, such parameters as polarity, viscosity, temperature, electric potential, local electric field, pressure, pH, etc., can be registered successfully using the modem sensitive apparatus for fluorescence detection [1, 4—12]. As a consequence, fluorescent molecules are used successfully as molecular probes to study the local characteristics of physicochemical, biochemical and biological systems. 

When suitable data sets are defined, different approaches can be used to codify the chemical information within chemical descriptors. Nowadays we have powerful tools to describe them in different ways by their physicochemical properties, surface properties, or their 3D fields generated by interactions with different chemical probes. Typically many chemical descriptors are calculated (up to thousands) and then the important ones are selected. We briefly explain some of the most common approaches used, trying to classify them in families to simplify the overview. 

The process of combining cyanine and squaraine dyes by encapsulation, or covalent or noncovalent attachment with macrocyclic hosts, macromolecules, and micro- or nano-particles is a promising way to design novel probes and labels with substantially improved properties and for the development of advanced fluorescence-based assays. Nevertheless, the physicochemical properties of these dye-compositions are strongly dependent on the dye structure as well as the nature of the host macrocycle, macromolecule, or particle. Finally, development of new methods to synthesize these tracers can also be considered a challenging task. 

As a consequence of the strong influence of the surrounding medium on fluorescence emission, fluorescent molecules are currently used as probes for the investigation of physicochemical, biochemical and biological systems. A large part of this book is devoted to the use of so-called fluorescent probes. 

The term responsive (elsewhere indicated as smart ) refers to diagnostic agents whose contrasting properties are sensitive to a given physicochemical variable that characterizes the microenvironment in which the probe is distributed (116-117). Typical parameters of primary diagnostic relevance include pH, temperature, enzymatic activity, redox potential and the concentration of specific ions, and low-weight metabolites. 

In the initial phase of our work we prepared a set of benzyl esters of the 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (DVA) which were monosubstituted in the meta position. The substituents were chosen to cover a broad spectrum of physicochemical parameter space by selecting them from Hansch s cluster sets( ). In addition, substituents with no bridging group, one atom and two atom bridges were included to probe the need for a bridging atom. 

Abstract Piperazines and its congeners, (di)keto piperazines are valuable tools in drug discovery, providing a natural path for the process peptide > peptidomimetic > small molecule also called depeptisation. Moreover, they can provide molecular probes to understand molecular pathways for diseases of unmet medical need. However, in order to better understand the design of such value added compounds, the detailed understanding of scope and limitation of their synthesis as well as their 3D structures and associated physicochemical properties is indispensables. Isocyanide multicomponent reaction (MCR) chemistry provides a prime tool for entering the chemical space of (di)(keto)piperazines since not less then 20 different ways exist to access a diversity of related scaffolds. 

Cruciani et al., used a dynamic physicochemical interaction model to evaluate the interaction energies between a water probe and the hydrophilic and hydrophobic regions of the solute with the GRID force field. The VolSurf program was used to generate a PLS model able to predict log Poet [51] from the 3D molecular structure. 

To determine the structure of these different types of networks we have extensively studied (Ref. 1 and unpublished work) the diffusional behaviour of materials within these concentrated solutions. These diffusants are used in trace quantities so that they do not perturb the physicochemical properties of the network. By varying the size of the diffusional probe a good deal of information can be obtained about the structure of the network due to the hindrance effect the latter exerts on the diffusant. 

Tetrakis(acetato)ditungsten(II) is a very air-sensitive, bright yellow, diamagnetic solid. It is moderately soluble in THF and acetonitrile but solutions in the latter solvent decompose after several hours. The 360 MHz XH NMR spectrum (in THF-d8) consists of a single methyl resonance at S 2.91. The mass spectrum (solid probe, electron impact, 40-70-eV ionizing voltage) shows the parent ion multiplet at m/e 604. Other spectroscopic data and physicochemical properties are described in the literature.8... 

The binding of fluorescent probes of different hydrophobicities can be used to compare the surface properties of proteins in relation to their physicochemical properties, such as foaming and emulsifying. CPA (cfr-parinaric acid) has been used to study eleven food-related proteins, and the results have been compared with theoretical models for predicting foam capacity (Arteaga and Nakai, 1993 also see... 

---