Peter J. Sadler

Cisplatin Binding Sites on Human Albumin

Reactions of cisplatin (cis-[PtCl2(NH3)2]) with albumin are thought to play an important role in the metabolism of this anticancer drug. They are investigated here via (i) labeling of cisplatin with 15N and use of two-dimensional1H,15N NMR spectroscopy, (ii) comparison of natural human serum albumin with recombinant human albumin (higher homogeneity and SH content), (iii) chemical modification of Cys, Met, and His residues, (iv) reactions of bound platinum with thiourea, and (v) gel filtration chromatography. In contrast to previous reports, it is shown that the major sulfur-containing binding site involves Met and not Cys-34, and also a N ligand, in the form of an S,N macrochelate. Additional monofunctional adducts involving other Met residues and Cys-34 are also observed. During the later stages of reactions of cisplatin with albumin, release of NH3 occurs due to the strong trans influence of Met sulfur, which weakens the Pt-NH3 bonds, and protein cross-linking is observed. The consequences of these findings for the biological activity of cisplatin-albumin complexes are discussed.

Inorganic Chemistry and Drug Design

Publisher Summary This chapter discusses some of the current uses of inorganic compounds as drugs and diagnostic agents. It focuses on areas of demonstrated medical and clinical interest. The illustrative examples chosen are mostly concerned with metals and do not form a comprehensive list. The use of inorganic compounds in medicine dates back to ancient times. The wider use of inorganic compounds in health care depends heavily on overcoming the toxicity problem. Arsenic, for example, is widely perceived to be a toxic element, but the enormous variation in toxicity among the types of arsenic compounds is not widely acknowledged: As(III) compounds are usually much more toxic than As(V) compounds, and arsenobetaine (Me 3 As + CH 2 C0 2 − )is relatively nontoxic, which is fortunate because man consumes it regularly in certain fish and crustacea. The Egyptians are said to have used copper to sterilize water in 3000 BC, and the Chinese were using gold in medicine in 2500 BC; mercurous chloride was known to be a diuretic during the Renaissance period, and mercurial diuretics were widely used up until the 1950s.

Cadmium-Resistant Pseudomonas putida Synthesizes Novel Cadmium Proteins

Three cysteine-rich proteins of molecular weight 4000 to 7000, containing 4 to 7 gram atoms of cadmium, zinc, and copper per mole were isolated from Pseudomonas putida growing in 3 mM cadmium. The three proteins were induced during different phases of growth, and the smallest (molecular weight 3600; 3 gram atoms of cadmium) was released into the medium when the cells lysed. The results of amino acid analyses and of ultraviolet, circular dichroism, electron paramagnetic resonance, and cadmium-113 nuclear magnetic resonance spectroscopy suggest a novel cadmium(II)-zinc(II)-copper(I) cluster structure for the major protein.

Assignment of resonances for ‘acute-phase’ glycoproteins in high resolution proton NMR spectra of human blood plasma

Broad resonances at 2.04 and 2.08 ppm in 500 MHz Hahn spin‐echo 1H NMR spectra of human blood plasma are assigned to the N‐acetyl groups of mobile carbohydrate side‐chains (largely N‐acetylglucosamine and N‐acetylneuraminic acid) of glycoproteins such as α1,‐acid glycoprotein. Their intensities in spin‐echo spectra correlate with clinical conditions in which an elevation of the level of ‘acute‐phase’ glycoproteins is expected, and so may be of value in the study of certain diseases.

Phosphines and metal phosphine complexes: Relationship of chemistry to anticancer and other biological activity

Current interest in the biological chemistry of phosphines and their metal complexes ranges from the widespread application of PH3 as a fumigant, to the clinical use of a Au(I)PEt3 complex as an anti-arthritic drug. Metal phosphine complexes also offer potential as heart-imaging agents and anti-cancer drugs. Data on cytotoxicity and anticancer activity are surveyed in detail with particular emphasis on diphosphines and their copper, silver and gold complexes. Chemistry of likely relevance to pharmacology is discussed: especially redox reactions (disulphide reduction, oxygen abstraction), radical reactions and metal binding. Much phosphine chemistry of relevance to biology has yet to be explored.

Nuclear magnetic resonance studies of blood plasma and urine from subjects with chronic renal failure: identification of trimethylamine-N-oxide

We have used 1H-, 13C- and 14N-NMR spectroscopy to investigate the constituents of plasma and urine in 16 patients with chronic renal failure (CRF). Resonances not previously observed in spectra of plasma from healthy volunteers were seen in CRF plasma, including those for trimethylamine-N-oxide (TMAO) and dimethylamine (DMA). A possible analogy with the plasma of elasmobranch fishes, in which TMAO stabilizes proteins in the presence of very high urea concentrations, is noted. The intensity of the TMAO resonance for CRF subjects was correlated with the plasma concentration of urea (R = 0.55) and creatinine (R = 0.74), suggesting that the presence of TMAO is closely related to the degree of renal failure. When normal subjects ate a meal of TMAO-containing fish, TMAO appeared rapidly in the plasma and in the urine. Thus TMAO is efficiently cleared by the healthy kidney. Differences in the interaction of lactate with plasma proteins were detected by NMR, suggesting that uraemia impairs their transport roles.

Coordination chemistry of metallodrugs: insights into biological speciation from NMR spectroscopy

Abstract There is much current interest in the design of metal compounds as drugs and diagnostic agents and in understanding the molecular mechanisms of action of metallopharmaceuticals already in clinical use. Central to progress in this area is investigation of the speciation of metal compounds, especially in biological media such as cells, body fluids and cell culture media. Modern multinuclear NMR approaches are very powerful for investigation of the thermodynamics and kinetics of reactions of metal compounds with both small and large biomolecules and it is possible to study the coordination chemistry of metallodrugs under physiologically relevant conditions. For example [ 1 H, 15 N] inverse detection methods allow studies of intermediates in the pathways of DNA platination by anticancer drugs and the direct detection of sulphur adducts of platinum drugs in urine. Other applications which are discussed include ligand exchange reactions of gold antiarthritic drugs, copper, silver, gold and ruthenium anticancer agents and bismuth antiulcer drugs. Resolution enhancement, specific isotopic labelling of amino acid side-chains and high field NMR studies of metal nuclei provide insight into the uptake and release of metallopharmaceuticals from the blood plasma proteins albumin (66 kDa) and transferrin (80 kDa). The use of 31 P cross-polarization magic angle spinning NMR spectroscopy to investigate the structures of bioactive metal phosphine complexes in the solid state is also described.

The structure of the antitumor complex cis-(diammino) (1,1-cyclobutanedicarboxylato)-Pt(II): X ray and nmr studies

X-ray crystallography shows that Pt(NH 3 ) 2 (CBDCA) is a square-planar complex with the dicarboxylate chelate ring in the boat conformation and a planar cyclobutane ring. 1 H and 13 C nmr studies suggest that rapid chelate ring flipping occurs in solution. The value of 195 Pt nmr combined with 15 N labeling as an informative new method of studying carboxylate coordination is illustrated. nmr results are also reported for the analogous ethylmalonate complex.

Gold drugs: Mechanism of action and toxicity

Gold drugs are still amongst the most efficacious for the treatment of rheumatoid arthritis. Their mechanism of action, as well as the molecular basis of their side-effects, remain poorly understood. Current theories are reviewed, including recent potential breakthroughs. The interaction of gold(III) with peptides and proteins and its immunochemical implications are discussed.

NMR-invisible lactate in blood plasma

Resonances for lactate are broadened in 500 MHz 1H NMR spectra of human blood plasma and only about one‐third is visible in Hahn spin‐echo spectra. Similar effects are observed for some other carboxylate anions. Lactate added to the high‐M r fraction of plasma can give rise to peaks which are too broad to observe in either single‐pulse or spin‐echo spectra. Addition of agents such as NH4Cl of SDS dramatically increases the intensities of lactate peaks. Some glycoproteins appear to broaden lactate resonances.