The effect of anesthetics on hydrogen bonds. An infrared study at low anesthetic concentrations

Molecular surface electrostatic potentials and anesthetic activity

General anesthetics apparently act through weak, noncovalent and reversible interactions with certain sites in appropriate brain proteins. As a means of gaining insight into the factors underlying anesthetic potency, we have analyzed the computed electrostatic potentials V (S)(r) on the surfaces of 20 molecules with activities that vary between zero and high. Our results are fully consistent with, and help to interpret, what has been observed experimentally. We find that an intermediate level of internal charge separation is required; this is measured by Pi, the average absolute deviation of V (S)(r), and the approximate window is 7 < Pi < 13 kcal mol(-1). This fits in well with the fact that anesthetics need to be lipid soluble, but also to have some degree of hydrophilicity. We further show that polyhalogenated alkanes and ethers, which include the most powerful known anesthetics, have strong positive potentials, V (S,max), associated with their hydrogens, chlorines and bromines (but not fluorines). These positive sites may impede the functioning of key brain proteins, for example by disrupting their normal hydrogen-bond patterns. It has indeed been recognized for some time that the most active polyhalogenated alkanes and ethers contain hydrogens usually in combination with chlorines and/or bromines.

Mechanisms of general anesthesia: from molecules to mind

Despite the widespread presence of clinical anesthesiology in medical practice, the mechanism by which diverse inhalational agents result in the state of general anesthesia remains unknown. Over recent decades, our understanding of general anesthetic mechanisms has evolved dramatically from early unitary hypotheses, largely due to the development and influence of a myriad of scientific disciplines ranging from molecular biology to cognitive neuroscience. These discoveries have led to a renaissance of investigation into the mechanisms of general anesthetics and have generated both novel answers and questions. In this chapter, we review the major hypotheses of general anesthetic mechanisms of action and present an expanded overview of current investigation into those mechanisms. We also present a framework to aid in thinking about the actions of these agents, highlighting the relationship between putative targets at the molecular level and the more integrated functional changes in behavior and consciousness.

The Site of Action of General Anesthetics - A Chemical Approach

Recently Urban (Br. J. Anaesth. 2002, 89, 167) and Trudell (Br. J. Anaesth. 2002, 89, 32) assessed the present state of the art in anesthesiological research. This article is an attempt to add to the discussion some ideas from the chemist's point of view. General anesthesia is a matter of molecular associations. Among the intermolecular interactions that can be involved, weak hydrogen bonding and van der Waals forces are believed to be most important. A pluralistic view is proposed, thereby different anesthetics can choose different interactions in conformity with their chemical structure. This can involve proteins, lipids, and sugars. Special attention is given to glycoproteins and glycosphingolipids. A review with 90 references.

Role of hydrogen bonding in general anesthesia

The importance of hydrogen bonding in determining the potency of a general anesthetic is controversial. In order to investigate the role of hydrogen bonding further, we have used a multiple linear regression approach to quantify the relative importance of various physical properties of an anesthetic molecule (i.e., its ability to donate or accept a hydrogen bond, its dipolarity and polarizability, and its size) in determining its anesthetic potency. For comparison, we have applied the same approach to partitioning between water and three simple, but contrasting solvents (n-octanol, n-hexadecane, and N,N-dimethylacetamide) and to inhibition of an enzyme (firefly luciferase) which mimics many of the properties of general anesthetic target sites in animals. We present equations which accurately predict potencies (over many orders of magnitude) for producing general anesthesia and inhibiting the firefly luciferase enzyme. We find that the aqueous potency (defined as the reciprocal of the aqueous EC50 concentration) of a molecule as a general anesthetic or an inhibitor of luciferase is determined overwhelmingly by its size (which increases potency) and its ability to accept a hydrogen bond (which decreases potency), but only marginally by its ability to donate a hydrogen bond or by its dipolarity and polarizability. We conclude that general anesthetic target sites in animals must have, in addition to their overall hydrophobicity, a polar component which is a relatively poor hydrogen bond donor, but which can accept a hydrogen bond about as well as water.