# Tag Info

16

Charge separation at waterfalls with airborne ions, resulting in a potential between the base of the waterfall and the surrounding air, is a phenomenon examined by Philipp Lenard (Über die Elektrizität der Wasserfälle, Ann Phys (Leipz), 1892, 46, 584–636). The effect is real and more recent field studies, such as Characterization of ions at Alpine ...

15

Although I can't think of any drug examples other than thalidomide, here's information on thalidomide's mechanism: The chiral carbon of thalidomide can tautomerize in basic conditions into an enol, which is achiral. A reversal back to the ketone results in a mix of (R) and (S) enantiomers. In the body, this tautomerization is generally catalyzed by basic ...

14

A definitive reference is: "The Many Roles for Fluorine in Medicinal Chemistry" J. Med. Chem., 2008, 51 (15), 4359–4369. In reference to the bullet points: Fluorine obviously affects $\ce{p}{K_{a}}$ and can make an acid stronger but also a base weaker which could be advantageous when optimising a drug candidate (lead) molecule. I guess here they refer to $... 10 One of the perhaps most important theory of anaesthesia is that: Most anaesthetics enhance the activity of inhibitory GABAa receptors and other cys-loop ligand-gated ion channels. Other important effects are the activation of a subfamily of potassium channels (the two-pore domain K+ channels) and inhibition of excitatory NMDA receptors Almost all ... 10 In pharmaceutical industries,$56\%$of the drugs currently in use are chiral molecules and$88\%$of the last ones are marketed as racemates (or racemic mixtures), consisting of an equimolar mixture of two enantiomers. More recently, drugs originally marketed as racemic mixtures are reintroduced using the active isomer. Examples include racemic citalopram (... 10 The idea of a 'rotatable bond' is somewhat arbitrary, given that under the right conditions basically any bond can be rotated. When thinking about concepts in medicinal chemistry like rotatable bonds, its therefore important to make sure you're working with the definition used when defining the rule. The original Veber papers (J. Med. Chem. 2002, 45, 2615) ... 9 Plaques are continually being removed from arteries by natural mechanisms within the body. Statin use, when combined with aggressive dietary changes, can slow down the rate of plaque deposition to the point that the rate of plaque removal is actually higher than the rate of plaque deposition, and, as a consequence, plaque thinning can be observed. Reducing ... 9 Ageing is a disease. Just as treatments have been found for other diseases, ageing can be slowed or reversed as well. Not that long ago, scientists noticed that at the end of each DNA strand there were thousands of nucleotides. Nucleotides are used for genetic coding. That is to say, certain sequences of nucleotides instruct the body to synthesize ... 8 The basic idea is sound, and is used to some degree; however, there are significant difficulties inherent in "tailoring" a chemical to selectively target certain organisms and not others. There are three things that a chemical can do that make it toxic to cellular life: Rip some vital chemical to shreds. Chlorine and other light halogens (fluorine, iodine)... 8 Organotin compounds are rather toxic. They are also persistent in the environment and have a long biological half-life. The problem is that trialkyltin byproducts from your reaction are difficult to separate from the product. In the lab, this is painful and (usually) involves multiple columns, but when you want to get a drug past the FDA into the clinic ... 7 This is lamotrigine, a sodium channel blocker prescribed against epilepsy. Apparently it's also prescribed for bipolar disorder. 7 Allergic reactions against dichromates are not uncommon. However, dichromates and chlorides, are two pairs of shoes. Really different ones, like stiletto heels and moon boots ;-) To my knowledge, there are no eye drops containing potassium dichromate! The sodium chloride that you mentioned is nothing but table salt. Isotonic solutions of sodium chloride ... 7 The half-life of$\ce{^{89}Sr}$is 50 days compared to a half-life of 29 years for$\ce{^{90}Sr}$. So a large enough dose of$\ce{^{90}Sr}$to be useful would leave the patient radioactive for the rest of his/her life. Edited for use of$\ce{^{89}Sr}$. In a comment Karl pointed out that the isotope is used to treat bone cancer. 6 I'm in a medicinal chemistry department, the floor below is the pharmaceutics department. We are both located in our university's college of pharmacy. The pharmacology department is under the college of medicine in same building as biochemistry, microbiology, etc. There is little interaction between departments here and that's not good. But we can break the ... 6 Question: When these foreign amines have been taken up into the vesicles how do they proceed?...Do they re-enter the synaptic cleft by exocytosis...How are they eventually cleared from the synaptic area? Here is the mode of action of these agents (indirectly acting sympathomimetics): The most important drugs in the indirectly acting sympathomimetic ... 6 Your predictions are right; the molecule has more basic character. The drug itself is practically insoluble in water, because the big organic molecule is near it's isoelectric point at the pure water's pH. However by protonating or deprotonating it and thus making it charged it's solubility is greatly enchanced. This is also the case with those medical ... 6 The commercial active pharmaceutical ingredient (API) is ciprofloxacin hydrochloride. This may explain why you refer to the pH range as 3.3 to 3.9. It's not uncommon for non-literature references to mention API's without mentioning them as a salt. 6 7-Hydroxymitragynine The extraction and crystallization of the parent alkaloid, mitragynine, from dried leaves of Mitragyna speciosa (Kratom), has been described in great detail by A. H. Beckett, E. J. Shellard and A. N. Tackie in Planta Med., 1965, 13, 241-246 (DOI). (Interestingly, the procedure also furnished speciofoline, a spiroindolo indolizidine ... 6 Is it less expensive? Yes, but not so much that it would be favored, i.e. you don't worry about saving \$5 when your doing a \$5000 procedure. Is there a particular property of barium that makes it a better contrast? No both absorb x-rays as a result of their high atomic numbers, in fact bismuth has more electrons per atom and thus is a better contrast ... 5 Here's a draft: First, read this paper. Considering we're under alkaline conditions (blood pH between 7.35-7.45) we'll take their alkaline mechanism proposal. Mechanism This is obviously incomplete, with good reason. Without knowing what the active site of the enzyme looks like (except for Ser70), it's difficult to devise of a mechanism. I could imagine ... 5 As stated in user208322's answer,$\ce{CH3}$and$\ce{H3C}\$ are exactly the same, they're only written differently for ease of reading. As per your question about how much truth there is to having 4 groups, it's 100% truth. You cannot have a chiral carbon that doesn't have 4 groups attached to it (i.e. must be sp3 hybridized). If you think you've found a ...

5

It's been suggested by Thomas Heimburg's group in Denmark (perhaps others) that anesthetics work by a common depression of the gel/fluid transition temperature in nervous membranes. Some virtues of this view include its consistency with the action of anesthetics being proportional to their partition in lipid (Meyer-Overton rule... and notice this rule ...

5

Well, firstly the capsule itself is not entirely insoluble. You can see this for yourself - if you drop one into water, it will start to dissolve very slowly and the water will turn cloudy. This process usually goes faster in the stomach, which has a very acidic environment, or the small intestine which is more alkaline. The capsule material is designed to ...

5

I have worked in natural product isolation a little. Although I have never witnessed tests with HeLa cells, I can provide some insight into the general screening procedure. In the lab I worked in which dealt with isolation of myxobacterial natural products, a novel strain was first tested as a crude extract in a preliminary screening via serial dilution ...

4

There are two misconception behind your question: You assume you can directly compare the colors of different compounds and derive oxidation states e.g of a heme (porphyrin) comparing to iron-oxide. No, it is not true. You assume this whole story has anything to do with copper. No, the blueish-green is nothing to do with copper, it is a (porphyrin) ...

4

Drugs racemised in-vivo The following table shows some of the most common (not an exhaustive list) of drugs racemised in-vivo. Since the biological targets are necessarily chiral, the molecules formed upon epimerisation (inversion at the centre being racemised) are usually inactive against the desired target (annoying, but ultimately fine), issues only ...

4

Chemists usually marks as biologically active compounds, that have clear effect on living being in small amounts. For example, methane is not biologically active, but potassium cyanide clearly is. Of course, the borderline is quite blurry and can move if context changes.

4

The Quantum Theory of Atoms in Molecules (QTAIM) provides a fairly unambiguous answer. First, I would like demonstrate the concept of an Atomic Basin. A region of space belongs to a given atom if the steepest ascent path through the electron density terminates at that atom. Consider a plane that contains the nuclei of the water molecule: and the atomic ...

Only top voted, non community-wiki answers of a minimum length are eligible