T he development of highly selective and sensitive analytical techniques has been a driving force for unprecedented advances in biotechnology, gene engineering, and drug discovery. Capillary electrophoresis (CE) is becoming a wider accepted analytical method in biology and medicine. CE offers short analysis time, high resolution, and minute consumption of samples and reagents, making it an attractive technique for mass bioassays and drug screening. Since the last Analytical Chemistry review in this field, 1 there have been published over 10 000 articles with CE as a topic. Within a variety of studies concerning CE, we have identified the intensively developing area of reversible biomolecular interactions which are defined as highly selective noncovalent binding of ligands with biomolecules. These affinity interactions control cell recognition, signal transduction, immune response, DNA replication, gene expression, and other cellular processes. The knowledge of quantitative parameters of binding reactions (equilibrium and/ or rate constants) is essential for understanding the mechanisms of biological processes, which these reactions regulate. The present review covers a 3-year period between January 2012 and November 2014. We have attempted to select studies that demonstrate the newest and most impactive developments in the field of biomolecular affinity interactions.

A linear asymmetric Pt(ii) trans-acetylide donor-bridge-acceptor triad designed for efficient charge separation, NAP[triple bond, length as m-dash]Pt(PBu3)2[triple bond, length as m-dash]Ph-CH2-PTZ (), containing strong electron acceptor and donor groups, 4-ethynyl-N-octyl-1,8-naphthalimide (NAP) and phenothiazine (PTZ) respectively, has been synthesised and its photoinduced charge transfer processes characterised in detail. Excitation with 400 nm, ∼50 fs laser pulse initially populates a charge transfer manifold stemming from electron transfer from the Pt-acetylide centre to the NAP acceptor and triggers a cascade of charge and energy transfer events. A combination of ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopies, supported by UV-Vis/IR spectroelectrochemistry, emission spectroscopy and DFT calculations reveals a self-consistent photophysical picture of the excited state evolution from femto- to milliseconds. The characteristic features of the NAP-anion and PTZ-cation are clearly observed in both the TRIR and TA spectra, confirming the occurrence of electron transfer and allowing the rate constants of individual ET-steps to be obtained. Intriguingly, has three separate ultrafast electron transfer pathways from a non-thermalised charge transfer manifold directly observed by TRIR on timescales ranging from 0.2 to 14 ps: charge recombination to form either the intraligand triplet (3)NAP with 57% yield, or the ground state, and forward electron transfer to form the full charge-separated state (3)CSS ((3)[PTZ(+)-NAP(-)]) with 10% yield as determined by target analysis. The (3)CSS decays by charge-recombination to the ground state with ∼1 ns lifetime. The lowest excited state is (3)NAP, which possesses a long lifetime of 190 μs and efficiently sensitises singlet oxygen. Overall, molecular donor-bridge-acceptor triad demonstrates excited state branching over 3 different pathways, including formation of a long-distant (18 Å) full charge-separated excited state from a directly observed vibrationally hot precursor state.

Photodynamic therapy that uses photosensitizers which only become toxic upon light-irradiation provides a strong alternative to conventional cancer treatment due to its ability to selectively target tumour material without affecting healthy tissue. Transition metal complexes are highly promising PDT agents due to intense visible light absorption, yet the majority are toxic even without light. This study introduces a small, photostable, charge-neutral platinum-based compound, Pt(II) 2,6-dipyrido-4-methyl-benzenechloride, complex 1, as a photosensitizer, which works under visible light. Activation of the new photosensitizer at low concentrations (0.1–1 μM) by comparatively low dose of 405 nm light (3.6 J cm−2) causes significant cell death of cervical, colorectal and bladder cancer cell lines, and, importantly, a cisplatin resistant cell line EJ-R. The photo-index of the complex is 8. We demonstrate that complex 1 induces irreversible DNA single strand breaks following irradiation, and that oxygen is essential for the photoinduced action. Neither light, nor compound alone led to cell death. The key advantages of the new drug include a remarkably fast accumulation time (diffusion-controlled, minutes), and photostability. This study demonstrates a highly promising new agent for photodynamic therapy, and attracts attention to photostable metal complexes as viable alternatives to conventional chemotherapeutics, such as cisplatin.

Current practical methods for finding the equilibrium dissociation constant, K d ,o fp rotein-small molecule complexes have inherent sources of inaccuracy.I ntroduced here is "accurate constant via transient incomplete separation" (ACTIS), which appears to be free of inherent sources of inaccuracy.C onceptually,as hort plug of the pre-equilibrated protein-small molecule mixture is pressure-propagated in ac apillary,c ausing fast transient incomplete separation of the complex from the unbound small molecule.Asuperposition of signals from these two components is measured near the capillary exit and used to calculate af raction of unbound small molecule,which,inturn, is used to calculate K d . Herein the validity of ACTIS is proven theoretically,i ts accuracy is verified by computer simulation, and its practical use is demonstrated. ACTIS has the potential to become ar eference-standardm ethod for determining K d values of protein-small molecule complexes.Reversible binding of proteins (P) to small-molecule ligands (L) plays an important role in the regulation of cellular processes. [1] In addition, most therapeutic targets are proteins, [2] and drugs are developed to form stable PL complexes with them:Complex stability is characterized by the equilibrium dissociation constant K d ,which is defined as:

We report on the results of a detailed quantitative experimental evaluation of exciton relaxation pathways as well as direct measurement of singlet oxygen (1O2) generation efficiencies for CdSe/ZnS quantum dot (QD)– porphyrin nanocomposites in toluene at 295 K. QD photoluminescence quenching in nanocomposites is caused by two main factors: electron tunneling in the quantum confined QD (efficiency 0.85–0.90) and Förster resonance energy transfer (FRET) QD→porphyrin (quenching efficiency 0.10–0.15). Efficiencies of 1O2 generation γΔ by nanocomposites are essentially higher with respect to those obtained for QDs alone. For nanocomposites, the nonlinear decrease of 1O2 generation efficiency γΔ on the laser pulse energy is caused by nonradiative intraband Auger processes, realized in the QD counterpart. Finally, FRET efficiencies found from the direct sensitization data for porphyrin fluorescence in nanocomposites (ΦFRET = 0.14 ± 0.02) are in good agreement with the corresponding values obtained via the direct 1O2 generation measurements at low laser excitation (ΦFRET Δ = 0.12 ± 0.03). The obtained quantitative results provide for the first time strong evidence that a FRET process QD→porphyrin is the reason for singlet oxygen generation by nanocomposites.