Job plot analysis

Very recently the first anion receptors 49 based on thiacalixarene units were reported [60] and their complexation abilities towards Cl anion were studied by XH NMR titrations in CDC13. The Job plot analysis clearly confirmed the formation of the 1 1 complexes, whilst the corresponding complexation constants depend on the length of alkylene chains on the lower rim. The lower the rigidity of the system (the longer chain), the weaker is the binding (compare Kc for 49a (3,480 M"1), 49b (1,900 M"1), 49c (1,790 M"1)). The comparison of 49a and 49d shows that the thioureido derivative is a slightly worse chloride receptor... 

A tetraamidinium functionalized, bowl-type cavitand (receptor 8) was developed by Diederich and Sebo [47]. This receptor was found to complex 1,3-dicarboxylate anions with good selectivity and a 1 2 binding stoichiometry both in CD3OD and D20, as revealed by standard Job plot analysis. In contrast, various nucleotide phosphates were found to be bound with a 1 1 stoichiometry in D20. In the case of the adenosine phosphates, the association constants increased as a function of nucleotide charge [i.e., the affinity order (K., M-1) was cAMP (1400) < AMP (10000)charged receptor (8) also showed moderate selectivity towards AMP (Ka = 10 000 M-1) over other nucleotide monophosphate anions, such as GMP (FCa = 5200 M-1), CMP (fCa = 3500 M-1), TMP (K l — 5900 M ), and UMP (Ka-3800M ) in D20 containing TRIS buffer (2.5 mM, pH 8.3). 

Row, Maitra and co-workers have linked two steroid subunits to synthesize macrocycle 66. The fluoride-binding properties of compoimd 66 were then investigated by a NMR titration experiment in CDCI3 at 22 °C, which found that the receptor bound fluoride with a 1 2 receptor/anion stoichiometry (a result confirmed by Job plot analysis) and stability constants of Ki = 1.8 ( 0.1) xlO M-i and K2 = 2.5 ( 0.35) xlO were found [79]. 

The equilibrium dialysis experiment revealed that histidine-substituted salicylamide was selected as an RNA ligand. Subsequent binding analysis by UV titrations and Job plot revealed the histidine-substituted salicylamide Cu + complex bound the target RNA hairpin with an apparent dissociation constant of 150 nM. This binding constant likely reflects more complex binding processes than a simple 1 1 interaction, as the observed binding curve saturates well below the concentration of the histidine-substituted salicylamide, and thus the actual affinity of the complex for targeted RNA is probably lower. Importantly, however, titrations with the... 

Aprotic solvents mimic the hydrophobic protein interior. However, a functional artificial receptor for flavin binding under physiological conditions must be able to interact with the guest even in competitive solvents. As found by spectroscopic measurements with phenothiazene-labeled cyclene, the coordinative bond between flavin and Lewis-acidic macrocyclic zinc in methanol was strong enough for this function. Stiochiometry of the complex was proved by Job s plot analysis. Redox properties of the assemblies in methanol were studied by cyclic voltammetry which showed that the binding motif allowed interception of the ECE reduction mechanism and stabilisation of a flavosemiquinone radical anion in a polar solvent. As a consequence, the flavin chromophore switched from a two-electron-one-step process to a two-step-one-electron-each by coordination. 

Shao and coworkers [61] have demonstrated that a noncovalent charge-transfer complex of calix[4]pyrrole-chloranil can be used as a chromogenic sensor for F and H2POj. Upon addition of calix[4]pyrrole 75 to the solution of chloranil 76 in chloroform, the color changed from pale yellow to blue. This indicated the formation of a charge-transfer complex between calix[4] pyrrole and chloranil in chloroform. The Job s plot analysis showed a 1 1 complex with... 

Results Summary for the UV-Visible/Job s Plot Analysis of Pyridine Binding to A, V -disal icy I aldehyde-1,3-prop ancdiimincnickel (II)... 

To obtain the formation constant, the number of metal-bound ligands, L or pyridine, must be independently determined. The Job s plot analysis in Experiment 3.6 revealed that a 1 1 Ni salpd-pyridine complex is formed we will assume this is the case. 

In the preceding expression, log(FJ is related to the depression of the fall-off curve at the center relative to the L-H expression in a og k/k ) vs. log(2f/(l -I- X)) plot. The values for F<. can then be related to the properties of specific species and reaction and temperature using methods discussed in Gardiner and Troe (1984). In Fig. 19, values of F for a variety of hydrocarbon decompositions are presented. As evident from this figure, in the limit of zero or infinite temperatures and pressures, all reactions exhibit Lindemann-Hinshelwood behavior and F approaches unity. From this figure, it is clear that L-H analysis generally does an adequate job in... 

An example of operator interaction with the primary analysis program, GPC, is shown in Figure 5. The job number assigned by the computer during sample definition is entered along with the detector selected for analysis. The operator then selects the baseline and the limits for data analysis by entering the times of the desired points. The plots desired and the disposition of the report file are chosen. The most recent calibration curve on file for the column set is used by default but others may be selected at the operator s option. 

In order to confirm formation of the oT15/oA15 duplex, additional techniques were used to characterize the complex. Stoichiometery analysis (Job s plot binding) supported the formation of a 1 1 complex. CD-assisted melting experiments performed on the... 

And so we purify the macromolecules, analyse them by breaking them down into their constituent parts, study their structure, and plot the sequence in which the units are joined together. The job of biochemistry as analysis stops there. When, finally, we can put the molecule back into the cell from which it came and try to describe how and why it behaves as it does in any particular biological situation, then we have entered another phase of research. 

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