Our desire to understand how the individual molecules that make up cells organize, interact, and communicate to form living systems has lead to the burgeoning field of chemical biology, an interfacial area of science that combines aspects of chemistry — the study of matter and its transformations, and biology — the study of living things and their interactions with the environment. The defining feature of chemical biology is the use of chemical approaches and small molecules to interrogate or manipulate biology.1,2 These small molecules are synthetic or naturally occurring ones that, for example, bind to DNA to affect protein expression levels, bind to proteins to inhibit their function, interact with lipids to alter membrane integrity, or become fluorescent in response to a metabolic event. Because small molecules can affect biochemical function, there is a clear link between chemical biology and pharmacology and medicine.3 While small molecules are usually implied as being organic compounds,4 inorganic small molecules also have a long history in both biology and medicine. Ancient civilizations used gold and copper for healing purposes, and the modern era of drug discovery was ushered in when arsenic-containing salvarsan was discovered as an anti-syphilis agent to become the world’s first blockbuster drug.5 Inorganic compounds should therefore not be overlooked in the realm of chemical biology, since their distinctive electronic, chemical, and photophysical properties render them particularly useful for a variety of applications.6-8

What are the properties of metal ions that impart utility to biology? Because inorganic elements comprise the bulk of the periodic table, the diversity of these properties is likewise broad and has been thoroughly covered by several books in the field of bioinorganic chemistry.9-11 A brief summary of the general chemical properties of metals is given below.


Charge. Metal ions are positively charged in aqueous solution, but that charge can be manipulated depending on the coordination environment so that a metal complexed by ligands can be cationic, anionic, or neutral.


Interactions with ligands. Metal ions bind to ligands (both organic and inorganic) via interactions that are often strong and selective. The ligands impart their own functionality and can tune properties of the overall complex that are unique from those of the individual ligand or metal. The thermodynamic and kinetic properties of metal—ligand interactions influence ligand exchange reactions.


Structure and bonding. Metal—ligand complexes span a range of coordination geometries that give them unique shapes compared to organic molecules. The bond lengths, bond angles, and number of coordination sites can vary depending on the metal and its oxidation state.


Lewis acid character. Metal ions with high electron affinity can significantly polarize groups that are coordinated to them, facilitating hydrolysis reactions.


Partially filled d-shell. For the transition metals, the variable number of electrons in the d-shell orbitals (or f-shell for lanthanides) imparts interesting electronic and magnetic properties to transition metal complexes.


Redox activity. Coupled with the variability of electrons in the d-shell is the ability for many transition metals to undergo 1-electron oxidation and reduction reactions.





Biology has taken advantage of these chemical properties of metals to perform several functional roles, which are summarized in Table 1. This is by no means an exhaustive list, but rather a primer to highlight important themes. Some metal ions, particularly the alkali and alkaline earth metals, are stable in aqueous solution as cations, making Na+, K+ and Ca2+ ideal for maintaining charge balance and electrical conductivity.10 On the other hand, the distinct architectures accessible via metal—ligand bonding interactions impart important structural roles to metal ions that encompass both macroscopic structural stabilization, as in biomineralized tissues,12 as well as molecular structural stabilization, as in proteins and nucleic acids that are stabilized in a preferred fold by metal ions.13-16 Metal—ligand bonding is also significant in its reversibility. For example, Nature takes advantage of reversible binding of metal ions like Ca2+ and Zn2+ to proteins or other storage repositories in order to propagate various biochemical signals.13,17 Metal ions themselves can be their own signal to adjust DNA transcription, as in the case of metalloregulatory proteins.18,19 Reversible metal—ligand coordination is also exploited to bind and release molecules to and from a metal center, a prime example being O2 binding and release from hemoglobin.

Table 1

Functional roles of inorganic elements found in biology, with selected representative examples.

/pdf/application-of-metal-coordination-chemistry-to-explore-and-2rsc5c6hy4.pdf

Application of metal coordination chemistry to explore and manipulate cell biology.

http://www.if-pan.krakow.pl/pjp/pdf/2009/1_154.pdf

Anthracycline-induced cardiotoxicity: Overview of studies examining the roles of oxidative stress and free cellular iron

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

/pdf/iron-behaving-badly-inappropriate-iron-chelation-as-a-major-229l082exr.pdf

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The role of mitochondria in protection of the heart by preconditioning

SIH—a novel lipophilic iron chelator—protects H9c2 cardiomyoblasts from oxidative stress-induced mitochondrial injury and cell death

Background— 5′AMP-activated protein kinase (AMPK), a well-known regulator of cellular energy status, is also implicated in ischemic preconditioning leading to cardioprotection. We hypothesized that AMPK is involved in anesthetic-induced cardioprotection and that this activation is mediated by reactive oxygen species (ROS). Methods and Results— Isolated Langendorff-perfused rat hearts were subjected to 35 minutes of global ischemia (I) followed by 120 minutes of reperfusion (I/R). Hearts were assigned to a control group (Con) or a sevoflurane (Sevo) group receiving 3 times 5-minute episodes of sevoflurane (2.5vol%) before I/R. Phosphorylation of both AMPK and endothelial nitric oxide synthase (eNOS) were determined by Western blot analysis. Cardioprotection was assessed after I/R from recovery of left ventricular pressure and from infarct size (triphenyltetrazolium chloride staining). In the control group, ischemia resulted in a 2-fold increase in phosphorylation levels of AMPK (Con 0.13±0.01 versus Con-I ...

/pdf/reactive-oxygen-species-induced-stimulation-of-5-amp-1xunesfkxu.pdf

Reactive Oxygen Species–Induced Stimulation of 5′AMP-Activated Protein Kinase Mediates Sevoflurane-Induced Cardioprotection

Background: In the current study, the authors investigated the distinct role and relative order of protein kinase C (PKC)-δ, adenosine triphosphate-sensitive mitochondrial K + (mito K + ATP) channels, and reactive oxygen species (ROS) in the signal transduction of sevoflurane-induced cardioprotection and specifically addressed their mechanistic link. Methods: Isolated rat trabeculae were preconditioned with 3.8% sevoflurane and subsequently subjected to an ischemic protocol by superfusion of trabeculae with hypoxic, glucose-free buffer (40 min) followed by 60 min of reperfusion. In addition, the acute affect of sevoflurane on PKC-δ and PKC-e translocation and nitrotyrosine formation was established with use of immunofluorescent analysis. The inhibitors chelerythrine (6 μM), rottlerin (1 μM), 5-hydroxydecanoic acid sodium (100 μM), and n-(2-mercaptopropionyl)-glycine (300 μM) were used to study the particular role of PKC, PKC-δ, mito K + ATP, and ROS in sevoflurane-related intracellular signaling. Results: Preconditioning of trabeculae with sevoflurane preserved contractile function after ischemia. This contractile preservation was dependent on PKC-δ activation, mito K + ATP channel opening, and ROS production. In addition, on acute stimulation by sevoflurane, PKC-δ but not PKC-e translocated to the sarcolemmal membrane. This translocation was inhibited by PKC inhibitors and ROS scavenging but not by inhibition of mito K + ATP channels. Furthermore, sevoflurane directly induced nitrosylation of sarcolemmal proteins, suggesting the formation of peroxynitrite. Conclusions: In sevoflurane-induced cardioprotection, ROS release but not mito K + ATP channel opening precedes PKC-δ activation. Sevoflurane induces sarcolemmal nitrotyrosine formation, which might be involved in the recruitment of PKC-δ to the cell membrane.

Reactive Oxygen Species Precede Protein Kinase C-δ Activation Independent of Adenosine Triphosphate–sensitive Mitochondrial Channel Opening in Sevoflurane-induced Cardioprotection

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of cardiac output.

Study Objectives: To compare the Nexfin cardiac output (CO) with the CO obtained from transthoracic Doppler echocardiography (TTE) during routine cardiac function screening. Design: Observational clinical study. Setting: Echocardiography laboratory. Patients: 40 ASA physical status 1 and 2 patients scheduled for routine TTE examination. Interventions: None. Measurements and Main Results: In 40 patients scheduled for routine TTE examination, we obtained simultaneous CO measurements with Doppler ultrasound and derived from Nexfin blood pressure measurements. Correlation and level of agreement between Nexfin and TTE were analyzed using Pearson correlation coefficient and Bland-Altman plots. The Pearson correlation coefficient for Nexfin versus TTE was 0.68 (CI: 0.46 - 0.82, P b 0.0001). Bland-Altman analysis showed a bias of 0.51 ± 1.1 L/min and limits of agreement of -1.6 to 2.6 L/min, with a percentage error of 39%.

R. Arthur Bouwman

Papers

SIH—a novel lipophilic iron chelator—protects H9c2 cardiomyoblasts from oxidative stress-induced mitochondrial injury and cell death

Reactive Oxygen Species–Induced Stimulation of 5′AMP-Activated Protein Kinase Mediates Sevoflurane-Induced Cardioprotection

Reactive Oxygen Species Precede Protein Kinase C-δ Activation Independent of Adenosine Triphosphate–sensitive Mitochondrial Channel Opening in Sevoflurane-induced Cardioprotection

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of cardiac output.

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of