Properties of Poisons - PDF

Here is the text from the image converted into a structured markdown format. # Properties of Poisons ### History Stuff **Arsenic:** * Wrt mechanism of action, there are many ways that arsenic disrupts biochemical functions including: Oxidative stress, phosphorus "mimic", enzym inhibition **Mary...

Here is the text from the image converted into a structured markdown format. # Properties of Poisons ### History Stuff **Arsenic:** * Wrt mechanism of action, there are many ways that arsenic disrupts biochemical functions including: Oxidative stress, phosphorus "mimic", enzym inhibition **Mary Blandy Case:** * First to utilize chemical testing * As used to poison her dad who disapproved of her marriage to a married man **Mathieu Orfila:** * "Father of toxicology" * Helped develop tests for the presence of blood in a forensic context and is credited as one of the first people to use a Microscope to assess blood and semen stains * Famous for his use and understanding of the Marsh test **Marsh Test** * Suspected sample of arsenic is mixed w/ $H_2SO_4$ and $Zn$ * Solution will bubble as gas is produced. * Gas is allowed to build up and then released * Gas is ignited by a flame proximal to a porcelain dish. If metal deposits form on the dish, there is arsenic * Zinc reduses $As^{3+}$ to $As^{3-}$ * As is protonated in acid to form arsine gas which thermally decomposes to produce $As_{(S)}$ **Everything Can be Toxic** * Paracelsus: "all things are puison and nothing is without poison; only the dose permits something not to be poisonous" * See woman who died of water toxicity for a Wii * Modern Toxicology * focuses on the changing nature of society's interaction w/ chemicals * Today's concern is less about lethal quantities of relatively benign substances; rather about pollutants in food, water and air * Contemporary fox focuses on: 1. Spread of contaminants and chemicals globally 2. increase in chemical contaminant diversity 3. Complications presented by Subtle yet enduring toxic responses * When a chemical, toxic or benign, Contacts a bidogical organism, the contact is known an exposure * When administered medically it is a dose **Toxicokinetics** * Study of the movement of an exogenous chemical from absorption, through distribution land to its final disposition via metabolism & excretion * Relies on quantifying the time course of disposition of a toxicant in the body * Reflects how the body handles toxicants as Indicated by the plasma concentration at various time points * The end result of these processes is a biologically effective dose of the toxicant * Amount of absorbed compound that reaches targets or sites of action to cause a biologic effect * Effects are result of the interaction of the biologically effective dose of the ultimate active form of the toxicant w/ a molecular target w/in the body **Toxicokinetic Steps** * Absorption: entry of toxicants through external membrane barriers into circulation. * Distribution: movement of toxicants through circulatory fluids to specific organs and Hissues within the body poprodrugs can be bioactivated * Metabolism: Biochemical processes that convert original (parent) toxicant to various metabolites * Elimination: removal of toxicant or metabolites from the body **Toxicodynamies** * Adverse effects produced by the xendaiotic and the mechanism * Glycoalkaloids and organophosphates (etc.) inhibit acetylcholinesterase which results in accumulation of acetylcholine * onstructive propagation of nerve signals we Ach is not broken down * Also disrupts call membranes by binding to Cholesterols **Overall Toxicological Process** * Toxicokinetics $\to$ metabolism $\to$ initiation $\to$ toxicodynamics **Toxicity** * Largely dictated by its physiochemical properties * A substance's lipophilicity, acid-base properties, and size all determine if a molecule can diffuse across all membranes & reach its target * Route of exposure can also have a profound effect on toxicity **Lipophiliciten** * Partition coefficient ($K_p$, $K_{ow}$) * relative lipophilicity us hydrophilicity * $Kaw = \frac{[organic phase]}{[aqueous phase]}$ * Molar concentration in 2-phase Solvent mixture at equilibrium * Log $K_{ow}$ is is proportional to lipophilicity * Yarger loykow = more lipophilic **Acid/Base** * Weak organic acids: * mostly neutral at pH < pka * Weak organic bases: * mostly neutral at pH>рка **Hydrophilic Toxins** * While lipophilic substances can easily permeate cell membranes to reach their target site, some heprophilic substances can cross membranes through different mechanisms * Some metal ions Can cross through protein Channels intended for other metals * molecular mimicry: Pb enter through Ca Channels & Hy binds to Son cysteine to mimic methionine * hydrophilic substances are poorly absorbed dermaly so generally need to be ingested or inhaled **Dose-Response Relationship** * Tests the capacity of the chemical to produce a discrete endpant in a population * Focus on rate in a population rather than individual response * Produces a sigmoidal curve * Threshold Concentration * Can be determined by dose-response relationship * Concentration at which the probability of an $Exposure\;lim. = \frac{NOAEL}{UF_1XUF_2}$ * adverse impact is low enough to be deemed acceptable * Threshold dose is a mathematical construct derived from NOAEL values determined from laboratory experiments on animals * No Observed Adverse Effect Level **General steps for setting exposure limits:** 1. Identify critical effects 2. Calculate threshold for critical effects 3. Apply uncertainty factors * Account for inter-species differences, interindividual differences Vit. A * Fat soluble suite of compounds, hard to excrete * Deficiency $=>$ impaired vision * High levels $=>$ death & organ development issues **Risk** * Chemical concentration & route of exposur + inherent toxicity **Lethal Dose** * $LD_{50}$: dose that causes death in 50% of the population * Alone cannol predict what is deadliest TCDD Poisoning * Polyhalogenated organic compounds that are Significant environmental pollutants * **Viktor Yushchenko** * Suspected acute TCDD porsoning * Chloracne-Scarred face * 50000-fol higer levels then ger. pop. **Molecules of Murder** * When it is tied to a crime * Use analytical techniques for detection and quant. * Must be strategically chosen and answer questions of legal interest in a timely Manher **Individualization** * Paul Kirk: "Criminalistics is the science of individualization" * Chemical identification serves to establish the Structure of an unknown compound * Forensics seeks to link chemical traces to a given person $\to$ chemical fingerprint * Mixture composition & impurity profich can help forense chemists individualze a Samph * If batch samples ave very pure, techniques like isotope racho MS can be employed which looks at characteristic variation on molecular Level * Individualization fallacy: a "match" does not mean the suspected object/person is the donor * Random match probability ### Detection & Quantitation * Identification, separation & quantification of chemical evidena can help answer questions of interest to a legal system * Can assist in the investigation and prosecution of criminals or absoe an innocent person from suspicion * Can be paramount in the resolution of complex criminal cases **Qualitative Chemical Analysis** * Provides confirmation on the presence of the chemical in a samph * eg. colometric tests like sodium rhodizonate * Generally does not provide useful information on the quantity of chemical **Chemical Analysis** * Provides information on the amount of analyte in the sample * Can be performed using a wide variety of methods instrumentation **Chromatography** * Founded by Michael Tswett in 1906 * Forensic samples are predominantly complex mixtures * Require separation * Enables the separation, identification, and purification of the components of a mixture for qualitative & quantitative analysis **Gas Chromatography** * A chromatographic technique where volatile compounds are separated * Samples are vaporized without thermal decomposition * Retention: Smaller more volatile compounds elute first * Higher BP = Stronger IMFs longer tr * Laver BP = Weaker IMFS => shorter tr * Detectors: FID (common) * Peaks in a chromatogram should be sufficiently resolved for accurate identification & quantitation Factors affecting resolution: * Column parameters * Selectivity (SP) * Flow rate Advantages: high res, low LODs, fast, accurate, reproducibl * Disadvantages: limited to volatile compounds, decomposition, destructive, incompatibh w/ ag. Samples, extensive prep **High-Performance Liquid Chromatography** * A technique where solubilized compounds are Separated and analyzed * Isocratic elution * Solvent comp. is constant * Gradient elution: * Solvent comp. changes * Can increase resolution & run efficiency * Normal phase: * Non-polar MP, polar SP * Reverse phase: * Polar MP, non-polar SP * Method of choice for pharmaceuticals * Under the same conditions, an analyte has a characteristic to that can aid in identification **Factors affecting HPLC resolution:** * то * Column parameters * Partich size * SP, MP * flow rate Advantages: RT performance, can use nouvolatile compounds non-destructive, flexible MP, less sample prep * Disadvantages: expensive, slower, incompatible w/ solvent analytes (eg. MeOH), laborious **Mass Spectrometry** * Used to identify & quantify a wide range of analytes * Measures mass-to-charge ratio (m/z) * Gold Standard = Chromatography + MS * Offers enhanced selectivity as it conveys info abt the MW of the analytes * While two analytes may share tr, it is unlikely for Hwo analytes to share a tr and MW 1. Ionization: Soft or hard ionization techniques * Soft: preseves parent peak (no fragmentation) * fragments important for analytes w/ same MW 2. Accelerations: ions accelerated to have same $E_x$ and will pass through into an ion beam, allowing the analyzer to start separating based on m/2 3. Deflection: a magnetic field will deflect ions based on their mass & Charge 4. Detection: a detector will quantify ions and produca a signal **Peak types:** * Base peak most abundant ion to which the spec. is normalized * Molecular ion peaks corresponds to MW * Daughter lons from fragmentation **Tandem MS** * 2+ MS connected to one another or a singh MS w/ multiple analyzers in series * Initial steps involve isolating the parent ion, which 13 then Subjected to further fragmentation to produce product rons * Greatly enhances selectivity and further facilitates Structural elucidation * Spectra can be compared to those in spectral libraries to see if it's a "match" **Derivatization** * Many compounds contain polar groups, limiting Compatabilitig w/ GC/MS * Derivatization conuerts a compound to a product to confer desireabh properties eg. volatilita * Examples include: silylation, acylation and alkylation * Also useful when the parent compound shows poor diagnostic ions for MS * Mass spectra w/ ions of higher m/2 ratios and abundance can be obtained, increasing specificity **Internal Standards** * Structurally similar but not identical to analyte of interest * Quantitative MS relies on IS * Also used for: identification of analyte ta & peak shape, injection vavianca, normalization of recovery differences, normalization of ionization effects **Spectroscopy** * Relies on analyte's interaction w/ light * Non-destructive * Specs split energy reflected by analyte into diff. 1 to produce a spectrum **UV-Vis Spec** * Measures amount of UV-Vis light absorbed * $I_{max}$ can be characteristic of compound of interest * Can be compared to reference spectra qualitatively **IR Spec** * Irradiate sample to stimulate vibrations * Useful for providing structural information * Only vibrations that result in changes in dipoh moment produa bands * Symmetrical bending/Stretching are inactive * Asymmetrical are IR active * Different groups absorb at different characteristic wavenumbers * Instrumentation is relatively inexpensive & portabh so analysis can easily be performed on scene * Can also be used quantitatively **Raman Spectroscopy** * ur laser and measuring the phIlluminating samphtons that undergo inelastic (raman) Scattering * Measures changes in polarizability * Can visualize homonuclear bonds that have faint IR activity * Not restricted to IR and can be used quantitativeh * More expensive but can be used on-site and requires very little or no prep ### Death & Decomp * Decomposition is a complex chemical process that begins immediately after death * Soft tissues decompose into simple organic matter over time * Proteins, lipids, sugars, nucleic acids & bone all decompose into a variety of products * Decomp. chemistry can be used in tandem w/ other forensic disciplines to extract important info **Establishing PMI** * Synergistic relationship between entomdogy and de camp. chemistry * Chemical techniques that study the fate of human remains in the environment have major implications in locating clandestine graves and assisting the estimate of postburial interval * Dr Vass, forse. pathologist, reported that an air sampling procedure demonstrated human decomp. and presence of chloroform controversial **Stages of Decomposition** 1. Fresh * Onset of autolysis + mortis' * Minimal percieved odor 2. Bloat * Onset of putrefaction * Gas accumulation due to microorganism & macromolecule breakdown * Strong percieved odor - Sulfur, $CH_3$,ammonia 3. Active decay * Deflation of body * High rate of tissue removal - liquefaction + disintegrat * Strong & complex odor 4. Advanced decay * Reduction in moisture * Some remaining tissue * Reduction in percieved odor 5. Dry remains * Hair, cartilage, bone remain * Mineral degradation * Reduad odor -mostly from Surrounding Soil * Generally decomposition occurs through the degrad of compounds in the body via reactive O species, enzymes, microorganisms, etc * Release of many liquids & gases * Tissue de comp breakdown of proteins, lipids and Carbs break down * Macromolecule degradation into structural componants * Most studies collect samples of fluids or volatiles above the body * Because the sample matrix is so complex, chrom. is important to understand the fundamental mechanisms involved w/ decomp * Decomp will begin very quickly after death * Decomposed tissue is first elassified as either preskeletonization or postskeletonization * In preskeletonized tissue, the first identifyabh process of decamp is autolysis * high conc. of ATP in cells - no $O_2$ so don't use * Intracellular pH decrease-lysosomes + pyruvate * In active decay, volatile fatty acids are produced from the breakdown of muscles & fat to produca phenolic compounds & glycerol * lots of putrescine & Cadaverine * Non-Chromatographic approaches to chemical decomposition Studies include soil analysis **Ninhydrin** * Release of nitrogen containing compounds from body will react w/ ninhydrin * Useful technique when paired w/ UV/Vis to locate Clandestine graves * Differenus in abs. exist dependent on sampling Site, attributed to narrow lateral diffusion of N influx in soil **Ninhydrin mechanism:** * Nucleophilic addition of amino acid to ketone * Dimerization which creates colour * Adipocere &Triglycerides * Adipocere forms from the neutral fats present in * soft tissue and can be found on decomposed remains & surrounding soil * DRIFT (IR) speč can be used to identify * Decrease in carbonyl band's associated wt triglycerides and an increase in bands relating to free fatty acids **Analysis** * Chromatographic studies on decomposition products were primarily used to identify chemical marks that could be used to estimate PMI * Orthogonal method can increase reliability **Static Headspace** * Sample of headspace abone evidenca is removed by syringes analyzed - fixed volume * Container is heated to volatilize compands * An airtight syringe is inserted to withdraw analytes * Injected into GC * Simple, nondestructive and fust * Suitable for low BP samples **Dynamic Headspace** * Gas flow is purged over sample and analytes in gas stream are collected & analyzed * Since ther is a purge flow, analytes must be trapped using a sorbent. * Use of sorbent w/o purge flow: passive concentration * Higher sensitivity + quantitative analysis but more laborious * Vitreous Humor * Potassium is the only enlectrolyte (analyzed in the (605) to increase after death * Linear relationship * Flame photometry - historical method * Capillary electrophoreols is now used wl UV detection * Complex buffer system but strong $R^2$ * low pressure IC with CD is now used as the std * Simple solvent system & cost effective **Ion Chromatography** * Similar to LC-MS but there is a charged SP that separates ions based on primary charge state and jonic radius * MPIS is ionic solution w/ sape polarity as analyte ions * Bound analytes are eluted by running a higher Concentration of ions through th The column * Hypoxanthine * Purine derivative created from degradation of adenosine * Similar to $K^+$, the compound is isolated from vitreous humour and is shown to have a linear relationship in [] up to 120h postmortem * Combine w/ $K^+$ for PMI estimate * HPLC methods offer greater sensitivity * Sequential injection analysis system to simultaneously quantify $K^+$ and Hx gives best goodness-of-fit **Fatty Acids** * Short chain volatile FAs from decomp. Can be found in Soil samples * Produced microbially * Use GC-MS for analysis * Require derivatization * Issues from complex matrix-ghosting, tailing **VOCs** * After death, a variety of gases & VOCs are emitted from the body-different VOC profile for each stage * VOCs can be characterized into the following chemical classes: sulfar, nitrogen, oxygen compounds, hydrocarbons, fluorids and chlorides * Common VOCs from the body include DMDS, toluene, hexane, 1,2,4 trimethylbenzene, 2-propanone, 3-pentanone, xylenes * In long term Ferm studies, benzene derivatives, halogenated compounds and aldehydes were most persistant * Most studies refer to the smell of death as a combination of the type and quantity of VOCS emitted unique to each body * Important to compare to controls **VOC Analysis** * analysis collect on a sorbent tube * Record lungth of time collected" * Desorb in thermal dyposition unit GCMS or 2DGC * Field portable scent transfer unit * Swept over bodies, drawing air and concentrating Sample onto absorbant surfac * Use SPME for GC-MS * VOC-Mobile soil probe * Stratified soil layer collection method * Useful for FIA and long chain aliphatic charact **SPME & HSSE** * Solid-Phase Micro Extraction and Head Space SorptiveExtraction * Volatile & semi-volatile compounds in the vapour phase become absorbed to the polymeric phase that coats the fused silica fiber * Absorption and resulting eqm is dependent on Sorben/analyte charateristics, concentration, to and finn * Analytes are desorbed from fiber for GC * HSSE uses Coated stir bar **2D GC** * Useful for characterizing VOCs * Uses 2 columns connected by a modulator which divides the elvent from the first column into a large number of small fractions, and then refocuses and reinjects them at regular intervals onto a Shorter second dimension column Allows for separation of VOCs that would co-lelute under standard circumstances **Soil vs Water vs Air** * Sample collection and extraction is important to consider * Matrix effects, persistence studies, environmental uptake, partitioning * Partitioning of VOCs between soil, water and air exists * Sample collection from only one matrixwill reduce the likelihood of obtaining the full profile of VOCs **Variables to Consider** * Establishing PMI is a complex analytical procedure * Variables to consider include:" * Differences in subject (human vs animal us tissue) * Variability in chemical composition of tissues * Stage of decomp * Sampling techniques * Instrumentation * Environmental factors * Van't Hoff's rule of Ten (velocity of ran increases 2 or more times w/ each 10% rise in To * Sample matrix * Geographic location Lack of literature on VOC analysis **Surrogate Studies** * Humane Surrogate studies tend to use pig, mice & cowως * Canines & Sniffer Technologies * When searching for clandestine graves: * Consider compounds that appear predominantly near body * Perform a background correction using enviro. controls * Consider geological aspects of grave site * Canines are used to track odour of human remains * (entrained using different tissues on faciting ng * SWG DOG OSAC * Scientific working groups os on canine detection of human remains * limited knowledge of error rates * Debuted validity * Extensive protocols * Published research needs include: * Methods for monitoring levels of contamination of aids * Development of reliabh surrogate aids * Evaluation of dissipation of odorant * Identification of odorant chemicals present in and above torgets * Integration of canim & instrumental detectors **Entomotoxicology** * Uses insects to detect presence of toxicological evidence in absence of direct forensic matrices **Overview of field suggests:** * Methods require standardization * Replication of studies need to be performed to decrease errors * Resources need to be integrated into the field * Studies need to cover entomological and tox. aspects * Standardization in method development and establishing optimized analytical protocols for detection and quantification are being worked on **Types of ideal feeding and reading substrate matrices should fit the following:"** * Toxicant should be stable & homogenously distributed throughout the matrix * Matrix should not react significantly ol toxicant * Matrit should be palatable, digestible and nutritions for target animal * Rearing matrix should be easy to handle, minimal to no odour and disposed easily * Production of matrix cost should be economical ## Natural Toxins **Toxins** * Compounds that are toxic/dangerous to living Organisms & occur naturally; technically, toxicants are Synthetic chemicals * Naturally occurring toxins can be further segregated into poisons which are chemicals that enter the body between the host and the victim and renoms which ane chemicals that are injected * Response to toxin ingestion can be as mild as an upset stomach, or as severe as death **Venam** * Cytotoxic * Causes immediate cell death * Proteolytic * Causes molecular structure of cells surrounding area of injection to degrade * Hemotoxic * Causes failure within the cardiovascular system * Neurotoxic * Causes failure within the nervous systun **Venom Toxicodynamics** Electrical signals are propagated in the brain and travel down the spinal cord to facilitate movement * Chemically, the nerve signals are created by the flow of ions * Opening and closing ion channels results in changes in * flow during an action potential * Energy produced by the Na/K ATPase pump * In order for the signal to be completed, the acetylcholinesterase cleaves Ach into acetate and a choline which will cause the end of the signal * Most neurotoxins disrupt this pathway at some point * eg. x-bungarotoxin prevents Ach reception \$\\ * B-bungurotoxin prevents release of vesicles that carry Ach from the Golgi apparatus **Snake Venom** * Venomous snakes inject prey w/ renom and wait until death or immobilization ocars * Venom is found in the parotid salivary glands on sides of head, below and behind eyes * Stored in alvedi and ejected through fangs * Complex mix and usually contains >20 compounds * Generally neurotoxins hemotoxins * Most are proteins & polypeptides * Polypeptides, aytotoxins, cardiotoxins, neurotoxins * Enzymes, L-amino acid oxidases, phosplipases, eta **Venom Toxicodynamics** * Some Snake venoms are hemotoxic and disrupt the cardiovascular system * Serine proteases mimic thrombin in the clotting cascade and lead to unstable blood clots subsequently dissolved by plasmin and depletes fibrin stores leading to susceptilality * to internal bleeding * Can also contain metalloproteases which damage the walls of blood vessels leading to leaks **Black Mamba** * Highly potent venom w/ synergistic toxins * $LD_{50}$: ~0.3mg/kg * Neurotoxins, Cardiotoxins, fasciculins, and calciseptine * Hyaluronidases facilitate dispersion in body * In general, neurotoxic venom is faster acting and more dangerous when compared to hemotoxic venom **Urushiol** * Natural poisons that lie within the body rely on exposure for toxic effects * Natural poisons can be removed from their host and still have a toxic impact **Urishiol** * is the oily compound produced by poison ivy, poison oak and poison Sumac * Produced internally in plant, found on leaves * fat solubh * allergic contact dermatitis Only Ing will cause an allergic reaction * Exposure possible via contact & inhalation * Attaches to certain proteins of the skin, where it acts as a hapten, leading to a type IV hypersensitivity reaction ### Botulinum * Neurotoxin secreted by bacteria * Works by binding to pre-synapse membrane of the nerve cells that secrete Ach * Prevents release * Low $LD_{50}$ (0.00001 mg/kg) with extremely narrow therapeutic margins **Tetrodotoxin** * Sodium channel blocker, inhibits action potential of neurons & axons * Binds to sitel of voltage-gated Na channel * Found naturally in tetradontiformes * $LD_{50}$ for mice is 334 Mylly for oral ingestion and 8 for injection **Plant Poisons** Bind to site I of voltage-gated Na Channel * There are several reported groups that used plant poisoned weapon tips * Egyptians coated arrow heads w/ sedatives & hypnotic toxins * Sacred texts of hinduism refer to aconite to poison arrow tips for war **Ricin** * Carbohydrate binding protein and highly potent toxin * estimated $LD_{50}$ of $Img/kg$ * Works by disabling ribosomes and inhibiting protein Synthesys * Severe aytotoxic effects, depurination via glycosylase **Gelsemine** * Alkaloid from yellow jasmim * Estimated dose to kill a 70kg human is 35mg * Kills within an hour (fatal Lose) * Binds strongly to and activates glycine receptors in nervous system * Causes $Cl^-$ to enter and redua release of Ach at synapse paralysis * Symptoms of giddiness, droopy eyelids, blurred /doubh vision and difficulty breathing **Curare** *Typically composed of isoquinoline or indole alkaloids leg. tubocurarine is a cyclic organic w/ an $NR_3$ grap * Bioavailability: 100%, protein binding: 50%, t1/2= 1-2 hrs * Only toxic if directly enters bloodstream * Muscle relaxant and will stop lungs from working asphyxiation * Blocks nicotonic acetylcholine receptor at neuromuscular junction * Antidote is thenfere AChE inhibitor **Hemlock** * Conine: alkaloid * L-conine is ex more deadly than D- * Recceptor is at synapse between neurons and blocks Ach receptors * Cicutoxin: found in water hemlock Blocks GABA receptionControls movement of $Ci^-$ and $K^+$ across mem brane * Death by respiratory failure **Microcystins** * Produced by blue-green algea * Potent inhibitors of protein phospatases in eukariotes * irreversibly inhibits protein phosphatases land 2½ * Buildup of phosphorylated proteins disrupt cyto Skeleton * Interact w/ mitochondria, causing dysfunction and production of reactive oxygen species **Half-Life (Biological)** * Time required for body burden/measure of exposure to decrease to ½ its peak/original measure * Applies when rate of elim. follows 1st order kin * Compounds wy Oth order kin. are more dangerous as they have a constant, slower rate of elimination **Natural vs Synthetic** * Some of the most toxic substances are from natural Sources * Some compounds tread the line between natural & Synth * Synthesized from precursors derived from natural Sources * Maintain structural similarity to natural precursorOpiates (extracted or refined) us opioids (synthesized) I have done my best to convert the image into a structured markdown format. 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