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Biomedical subjects

R S Brown

Publications and source records attributed to R S Brown.

At least 19 recordsLinked to original sources
PubMed2006

Hepatitis B treatment: Lessons for the nephrologist.

Hepatitis B affects approximately 350 million people worldwide, and an estimated 1.25 million people in the United States. Although most people infected with the virus do not develop significant hepatic disease from hepatitis B, 15-40% will develop serious complications. These complications include cirrhosis, the development of hepatocellular carcinoma , and hepatic decompensation. Patients with renal failure have increased risk of acquiring the virus through blood transfusions and contact with bodily fluids at hemodialysis centers, and of developing complications from hepatitis B virus infection. Renal transplant patients are at increased risk for exacerbations of hepatitis B with immunosuppression. Thus, it is crucial for the nephrologist to have a clear understanding of the natural history and treatment of hepatitis B, both pre- and post-renal transplant.

Algorithms↗
PubMed2006

Potentiometric titration of metal ions in ethanol.

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.

Journal Article↗
PubMed2006

Evaluating the evidence from clinical trials in chronic hepatitis C.

A number of studies are being published on investigational agents for the treatment of patients with chronic hepatitis C. Before incorporating new medications into therapy or electing to postpone therapy until an investigational agent receives regulatory approval, it is important to evaluate the following specific features of the published evidence: quality of the evidence, precision of the treatment effect, magnitude of the treatment effect, magnitude of the hazards, and other factors such as risk-benefit analysis and cost, including cost-effectiveness. Previous studies of treatment of patients with the disease allow us to establish some benchmarks and provide structure to evaluate the evidence of the efficacy and safety of these newer drugs.

Antiviral Agents↗
PubMed2005

Select utilization of obese donors in living donor liver transplantation: implications for the donor pool.

Living donor liver transplantation evolved in response to donor shortage. Current guidelines recommend potential living donors (LD) have a body mass index (BMI) <30. With the current obesity epidemic, locating nonobese LD is difficult. From September 1999 to August 2003, 68 LD with normal liver function test (LFTs) and without significant comorbidities underwent donor hepatectomy at our center. Post-operative complications were collected, including wound infection, pneumonia, hernia, fever, ileus, biliary leak, biliary stricture, thrombosis, bleeding, hepatic dysfunction, thrombocytopenia, deep venous thrombosis, pulmonary embolism, difficult to control pain, depression and anxiety. Complication rates for LD with BMI >30 (n = 16) and BMI <30 (n = 52) were compared. The incidence of wound infection increased with BMI, 4% for nonobese and 25% for obese LD (p = 0.024). There were no statistically significant differences for all other complications. No LD died. Recipient survival was 100% with obese LD and 80% with nonobese LD (p = 0.1). Select donors with a BMI >30 may undergo donor hepatectomy with acceptable morbidity and excellent recipient results. Updating current guidelines to include select LD with BMI >30 has the potential to safely increase the donor pool.

Adolescent↗
PubMed2004

La3+-catalyzed methanolysis of O,O-diethyl S-(p-nitrophenyl) phosphorothioate and O,O-diethyl S-phenyl phosphorothioate. Millions-fold acceleration of the destruction of V-agent simulants.

The La3+-catalyzed methanolysis of two phosphorothioate derivatives, O,O-diethyl S-(p-nitrophenyl) phosphorothioate (4a) and O,O-diethyl S-phenyl phosphorothioate (4b) were studied as a function of [La3+] and pH in methanol solvent. In both cases the kinetics of catalyzed methanolysis maximize at pH 9.1 and a detailed analysis indicates that the dominant species responsible for catalysis are dimers formulated as La3+(2)(-OCH3)2 and La3+(2)(-OCH3)4. The catalysis is compared with that seen for the corresponding phosphate esters, namely paraoxon (3a) and O,O-diethyl phenyl phosphate (3b) for which La3+ catalysis is slightly better and markedly worse than for 4a and 4b respectively. Overall, at s(s)pH 9.1, a 2 mmol dm-3 solution of La(OTf)3 with equimolar NaOCH3 provides accelerations of 2.2x10(8)-fold, 9.7x10(6)-fold and 9.3x10(6)-fold for methanolysis of 3a, 4a and 4b, relative to the background reaction of methoxide reacting with the three substrates. In each case, the P-containing product of the reactions is exclusively diethyl methyl phosphate. Turnover experiments with 6-fold and 100-fold excesses of 4a and 4b respectively, methanolyzed in the presence of approximately 10 mmol dm-3 La3+ and equimolar NaOCH3, indicate that the reactions are essentially complete within 103 s and 70 min respectively. The latter turnover experiment with 4b corresponded to 100 turnovers in 70 min and an overall reaction t1/2 of 8 min. A common mechanism of reaction is postulated for each of the substrates which involves Lewis acid coordination of one of the La3+ to the P=O unit, followed by nucleophilic attack by the second La3+-(-)OCH3.

Journal Article↗
PubMed2004

Zn2+-catalyzed methanolysis of phosphate triesters: a process for catalytic degradation of the organophosphorus pesticides paraoxon and fenitrothion.

The methanolyses of two neutral phosphorus triesters, paraoxon (1) and fenitrothion (3), were investigated as a function of added Zn(OTf)(2) or Zn(ClO(4))(2) in methanol at 25 degrees C either alone or in the presence of equimolar concentrations of the ligands phenanthroline (4), 2,9-dimethylphenanthroline (5), and 1,5,9-triazacyclododecane (6). The catalysis requires the presence of methoxide, and when studied as a function of added NaOCH(3), the rate constants (k(obs)) for methanolysis of Zn(2+) alone or in the presence of equimolar 4 or 5 maximize at different [(-)OCH(3)]/[Zn(2+)](total) ratios of 0.3, 0.5, and 1.0, respectively. Plots of k(obs) vs [Zn(2+)](total) either alone or in the presence of equimolar ligands 4 and 5 at the [(-)OCH(3)]/[Zn(2+)](total) ratios corresponding to the rate maxima are curved and show a nonlinear dependence on [Zn(2+)](total). In the cases of 4 and 5, this is explained as resulting from formation of a nonactive dimer, formulated as a bis-mu-methoxide-bridged form (L:Zn(2+)((-)OCH(3))(2)Zn(2+):L) in equilibrium with an active monomeric form (L:Zn(2+)((-)OCH(3))). In the case of the Zn(2+):6 system, no dimeric forms are present as can be judged by the strict linearity of the plots of k(obs) vs [Zn(2+)](total) in the presence of equimolar 6 and (-)OCH(3). Analysis of the potentiometric titration curves for Zn(2+) alone and in the presence of the ligands allows calculation of the speciation of the various Zn(2+) forms and shows that the binding to ligands 4 and 6 is very strong, while the binding to ligand 5 is weaker. Overall the best catalytic system is provided by equimolar Zn(2+), 5, and (-)OCH(3), which exhibits excellent turnover of the methanolysis of paraoxon when the substrate is in excess. At a concentration of 2 mM in each of these components, which sets the pH of the solution at 9.5, the acceleration of the methanolysis of paraoxon and fenitrothion relative to the methoxide reaction is 1.8 x 10(6)-fold and 13 x 10(6)-fold, respectively. A mechanism for the catalyzed reactions is proposed which involves a dual role for the metal ion as a Lewis acid and source of nucleophilic Zn(2+)-bound (-)OCH(3).

Catalysis↗
PubMed2003

La3+-catalyzed methanolysis of N-aryl-beta-lactams and nitrocefin.

The kinetics of the La(3+)-catalyzed methanolysis of N-phenyl-beta-lactam (2) and N-p-nitrophenyl-beta-lactam (3) as well as that of nitrocefin (1) were studied at 25 degrees C under buffered conditions. In the case of 2 and 3, the observed second-order rate constants (k(2)(obs)) for catalysis plateau at pH 7.5-7.8, reaching values of 1 x 10(-)(2) and 35 x 10(-)(2) M(-)(1) s(-)(1) respectively. Potentiometric titrations of solutions of 2 x 10(-)(3) M La(OTf)(3) were analyzed in terms of a dimer model (La(3+)(2)((-)OCH(3))(n)()), where the number of methoxides varies from 1 to 5. The species responsible for catalysis in the pH range investigated contain 1-3 methoxides, the one having the highest catalytic activity being La(3+)(2)((-)OCH(3))(2), which comprises 80% of the total La(3+) forms present at its pH maximum of 8.9. The catalysis afforded by the La(3+) dimers at a neutral pH is impressive relative to the methoxide reactions: at pH 8.4 a 1 mM solution of catalyst (generated from 2 mM La(OTf)(3)) accelerated the methanolysis of 2 by approximately 2 x 10(7)-fold and 3 by approximately 5 x 10(5)-fold. As a function of metal ion concentration, the La(3+)-catalyzed methanolysis of 1 proceeds by pathways involving first one bound metal ion and then a second La(3+) leading to a plateau in the k(obs) vs [La(3+)](total) plots at all pH values. The k(max)(obs) pseudo-first-order rate constants at the plateaus, representing the spontaneous methanolysis of La(3+)(2)(1(-)) forms, has a linear dependence on [(-)OCH(3)] (slope = 0.84 +/- 0.05 if all pH values are used and 1.02 +/- 0.03 if all but the two highest pH values are used). The speciation of bound 1 at a La(3+) concentrations corresponding to that of the onset of the kinetic plateau region was approximated through potentiometric titration of the nonreactive 3,5-dinitrobenzoic acid in the presence of 2 equiv of La(OTf)(3). A total speciation diagram for all bound forms of La(3+)(2)(1(-))((-)OCH(3))(n)(), where n = 0-5, was constructed and used to determine their kinetic contributions to the overall pH vs k(max)(obs) plot under kinetic conditions. Two kinetically equivalent mechanisms were analyzed: methoxide attack on La(3+)(2)(1(-))((-)OCH(3))(n)(), n = 0-2; unimolecular decomposition of the forms La(3+)(2)(1(-))((-)OCH(3))(n)(), n = 1-3.

Catalysis↗
PubMed2003

Billion-fold acceleration of the methanolysis of paraoxon promoted by La(OTf)3 in methanol.

The methanolysis of the insecticide paraoxon (2) was investigated in methanol solution containing varying [La(OTf)(3)] (OTf = (-)OS(O)(2)CF(3)) as a function of at 25 degrees C. Plots of the pseudo-first-order rate constants (k(obs)) for methanolysis as a function of [La(OTf)(3)](total) were obtained under buffered conditions from 5.15 to 10.97, and the slopes of the linear parts of these were used to determine the second-order rate constants (k(2)(obs)) for the La(3+)-catalyzed methanolysis of 2. Detailed analysis of the potentiometric titration data of La(OTf)(3) in methanol through fits to a multicomponent equilibrium mixture of dimers of general stoichiometry La(3+)(2)((-)OCH3)n, where n assumes values of 1-5, gives the equilibrium distribution of each as a function of. These data, when fit to a second expression describing k(2)(obs) in terms of a linear combination of individual rate constants k(2)(2:1), k(2)(2:2).k(2)(2:)n for the dimers, allow one to describe the overall catalytic profile in terms of the individual contributions. The most catalytically important species are the three dimers La(3+)(2)((-)OCH3)1, La(3+)(2)((-)OCH3)2, and La(3+)(2)((-)OCH3)3. The catalysis of the methanolysis of 2 is spectacular: a 2 x 10(-3) M solution of [La(3+)](total), at neutral, affords a 10(9)-fold acceleration relative to the base reaction (t(1/2) approximately 20 s at 8.2) with excellent turnover. A mechanism of the catalyzed reaction involving the La(3+)(2)((-)OCH3)2 species is proposed.

Chemical Warfare Agents↗
PubMed2003

Bis(pyridine)-based bromonium ions. Molecular structures of bis(2,4,6-collidine)bromonium perchlorate and bis(pyridine)bromonium triflate and the mechanism of the reactions of 1,2-bis(2'-pyridylethynyl)benzenebrominum triflate and bis(pyridine)bromonium triflate with acceptor olefins.

1,2-Bis(2'-pyridylethynyl)benzenebromonium triflate (4) and bis(pyridine)bromonium triflate (5) have been prepared and the mechanism of their reaction with various acceptors including eight alkenes of various structure, collidine, and Br(-) are reported. The reaction of 4 with neutral acceptors is second-order overall and involves a preequilibrium dissociation of the bidentate-bound Br(+) to form an unstable monodentate open form (4-op), which reacts with all neutral acceptors at or near the diffusion limit. Br(-) reacts with 4 by a different mechanism involving a direct nucleophilic attack on the Br(+). The reaction of 5 with acceptors proceeds by a dissociative mechanism to reversibly form an unstable intermediate (pyr-Br(+)), which reacts with 4-penten-1-ol, 4-pentenoic acid adamantylidineadamantane and cyclohexene with nearly the same selectivity. The crystal and molecular structures of bis(2,4,6-collidine)bromonium perchlorate (2-ClO(4)) and 5 were determined by X-ray crystallography.

Journal Article↗
PubMed2003

Proton inventory study of the base-catalyzed hydrolysis of formamide. Consideration of the nucleophilic and general base mechanisms.

An NMR study of the rates of hydroxide-promoted hydrolysis of formamide in aqueous media of varying mole fraction D(2)O (n) was performed at [LO(-)] = 1.42 M, T = 25 degrees C, to shed light on whether the mechanism involves a nucleophilic attack of HO(-) on the C=O or HO(-) acting as a general base to remove a proton from an attacking water. The solvent deuterium kinetic isotope effect under these conditions is inverse, k(OH)/k(OD) = 0.77 +/- 0.02 or k(OD)/k(OH) = 1.30 +/- 0.03. Proton inventory analysis of the k(n)() versus n data was undertaken through NLLSQ fits to equations representing four possible mechanisms encompassing nucleophilic and general base ones with waters of solvation on the attacking hydroxide, and with or without waters of solvation on the developing amide hydrate oxyanion. Both nucleophilic and general base mechanisms can be accommodated, but there are restraints on each that are discussed. The preferred mechanism is a nucleophilic one proceeding through a transition state having two solvating waters remaining on the attacking hydroxide and three additional waters attached to the developing amide hydrate oxyanion.

Acetates↗
PubMed2003

La(3+)-Catalyzed methanolysis of hydroxypropyl-p-nitrophenyl phosphate as a model for the RNA transesterification reaction.

The methanolysis of hydroxypropyl-p-nitrophenyl phosphate (HPNPP, 1) promoted by La(OTf)(3) under buffered conditions was studied in methanol as a function of pH at 25 degrees C. (31)P NMR studies at -90 degrees C indicate that there are at least three La/1 complexes formed at pH approximately 5.3 of 1:1, 2:2, and 1:2 stoichiometry. Kinetic studies of the observed pseudo-first-order rate constants for the methanolysis of 1 as a function of [La(3+)] at 4.5 < pH < 10.5 indicate there are two general pH regimes. In the low pH regime between 4.5 and 7.6, the plots of k(obs) versus [La(3+)] exhibit saturation behavior with very strong 1:1 binding, with a plateau rate constant that depends on [OCH(3)(-)]. The catalytically productive species is shown to be a 2:2 complex of La(3+) and 1, where the phosphate is proposed to be doubly activated, thereby promoting the methoxide reaction by some 4.6 x 10(10)-fold. In the high pH regime from 7.9 to 10.5, 1:1, 2:2, and 2:1 La(3+)/1 complexes are formed with the La(3+) coordinated in the form of [La(3+)(OCH(3)(-))](1,2). Throughout this pH regime at high [La(3+)], a saturation complex, (La(3+)OCH(3)(-))(2)/1, is formed that spontaneously decomposes with a rate constant of (5-10) x 10(-)(3) s(-)(1), leading to an acceleration of 10(9)-fold at pH 8.0.

Catalysis↗
PubMed2003

Europium ion catalyzed methanolysis of esters at neutral pH and ambient temperature. catalytic Involvement of Eu3+(CH3O-)(CH3OH)x.

The Eu(3+)-promoted methanolysis of three esters, p-nitrophenyl acetate (1), phenyl acetate (2), and ethyl acetate (3) is reported, as well as the potentiometric titration of Eu(3+) in MeOH at various [Eu(SO(3)CF(3))(3)] (SO(3)CF(3) = OTf). The titration data are analyzed in terms of two ionizations corresponding to macroscopic and values, which are respectively defined as the values at which the [CH(3)O(-)]/[Eu(3+)] = 0.5 and 1.5. As a function of increasing [Eu(OTf)(3)], increases slightly due to a proposed Eu(3+)/(-)OTf ion pairing effect, which tends to reduce the acidity of the metal-coordinated CH(3)OH, while decreases due to the formation of Eu(3+) dimers and oligomers which stabilize the (Eu(3+)(CH(3)O(-))(2))(n)forms through bridging of the methoxides between two or more metal ions. For ester 1, a detailed kinetic analysis of the reaction rates as a function of both [Eu(OTf)(3)] and in buffered methanol reveals that the /second-order rate constant (k(2)) plot for the catalyzed reaction follows a bell-shaped profile, suggesting that the active form is a Eu(3+)(CH(3)O(-)) monomer with a kinetic of 6.33 +/- 0.06 for formation and a of 8.02 +/- 0.10 for its conversion into the inactive (Eu(3+)(CH(3)O(-))(2))(n)oligomeric form. At higher values, plots of k(obs) vs [Eu(OTf)(3)] are linear at low metal concentration and plateau at higher metal concentration due to the formation of inactive higher order aggregates. The Eu(3+)(CH(3)O(-)) catalysis of the methanolysis of esters 1, 2, and 3 is substantial. Solutions of 10(-2) M of the catalyst at 7.12 accelerate the reaction relative to the methoxide reaction at that by 8 530 000-, 195 000 000- and 7 813 000-fold, respectively.

Journal Article↗
PubMed2003

Naphthalene and anthracene mineralization linked to oxygen, nitrate, Fe(III) and sulphate reduction in a mixed microbial population.

A microbial consortium from a mixture of garden soil and an enrichment of a coal-tar contaminated sediment mineralized naphthalene and anthracene when oxygen, nitrate, Fe(III) (soluble and insoluble) or sulphate were provided as terminal electron acceptors (TEAs). Rates of polyaromatic hydrocarbon disappearance and mineralization were similar in the presence of oxygen and nitrate, and slower with the other TEAs. A maximum mineralization of 37.5% naphthalene and 8.5% anthracene occurred in 30 and 160 days respectively when oxygen was provided as the TEA. On the other hand, only 9.5% naphthalene and 3.2% anthracene were mineralized in 42 and 160 days respectively with FeOOH. Mineralization occurred only when a TEA was provided and ceased when the naphthalene concentration decreased to non-detectable levels (less than 0.008 micromoles/L), as measured by fluorescence spectroscopy. CH4 was not detected in the headspace of any microcosm. These results showed that mineralization of polyaromatic hydrocarbons such as naphthalene and anthracene can be linked to wide range of TEAs demonstrating that intrinsic polyaromatic hydrocarbon bioremediation is possible if any of these TEAs were available.

Anthracenes↗
PubMed2002

Methanolysis of nitrocefin catalyzed by one and two Zn(2+) ions. A simplified model for class B beta-lactamases.

The methanolysis of nitrocefin (1) was investigated at 25 degrees C in anhydrous methanol as a function of [Zn(2+)] and as a model for the chemistry believed to occur in the active site of Zn(2+)(-)beta-lactamases. In the absence of metal ion, the vs rate constant profile shows a long plateau region having k(obs) = 9 x 10(-5) s(-1) between 7.5 and 12 generated after ionization of the COOH of 1 (kinetic pK(a) of 7.34) followed by attack of CH(3)O(-) with k(CH)3(O) = 1.18 M(-1) s(-1). Strong catalysis of the methanolysis is observed at all pH values between 7.95 and 11.34 in the presence of as little as 0.05-3 mM Zn(2+). Plots of the pseudo-first-order rate constant for methanolysis (k(obs)) as a function of reveal a saturation phenomenon indicative of formation of a 1:Zn(2+) complex, followed by a linear section indicative of the intervention of a second Zn(2+) ion in promoting the methanolysis of the complex. The two processes can be separated since the slope of the linear part of the plots gives the second-order rate constant (k(2)(obs)) for the second Zn process, while the intercept gives the spontaneous rate constant for methanolysis of 1:Zn(2+) (k(cat.)(obs)). A plot of log k(cat.)(obs) vs is bell-shaped, maximizing at 10, with ascending and descending domains both first order in [CH(3)O(-)]. A plot of log k(2) vs gives an ascending domain second order in [CH(3)O(-)], followed by a plateau above 9.5. The data are analyzed in terms of a one-Zn and two-Zn model in which the former involves rate-limiting attack of methoxide on a 1:Zn(2+) complex up to the maximum and a spontaneous reaction of 1:Zn(2+):(CH(3)O(-))(2), while the latter involves bimolecular attack of Zn(2+)(CH(3)O(-))(2) on both 1:Zn(2+) and 1:Zn(2+):(CH(3)O(-))(2). The relevance of these observations is discussed in terms of the currently accepted mechanism for hydrolyses of beta-lactams promoted by the Zn(2+)(-)beta-lactamases.

Algorithms↗
PubMed2002

Current methods of transfer of young people with Type 1 diabetes to adult services.

AIMS: To determine the efficacy and patient perception of various transfer procedures from paediatric to adult diabetes services. METHODS: Comparison between four districts in the Oxford Region employing different transfer methods, by retrospective study of case records and interviews of patients recently transferred from paediatric diabetes clinics. The main outcome measures were age at transfer, clinic attendance rates, HbA1c measurements and questionnaire responses. RESULTS: Two hundred and twenty-nine subjects (57% males) > 18 years old in 1998 and diagnosed with Type 1 diabetes < 16 years of age between 1985 and 1995, identified from the regional diabetes register. The notes audit was completed for 222 (97%) and 164 (72%) were interviewed by a single research nurse. Mean age at transfer was 17.9 years (range 13.3-22.4 years). Few young people were lost to follow-up at the point of transfer. There was a high rate of clinic attendance (at least 6 monthly) 2 years pretransfer (94%), but this declined to 57% 2 years post-transfer (P < 0.0005). There was large interdistrict variation in clinic attendance 2 years post-transfer (29% to 71%); higher rates were seen in districts where young people had the opportunity to meet the adult diabetes consultant prior to transfer. The importance of this opportunity was confirmed by questionnaire responses on interview. CONCLUSIONS: Adolescence is a vulnerable period for patients with diabetes. This regional survey demonstrated a marked decline in clinic attendance around the time of transition from paediatric to adult services. The reasons are complex, but mode of transfer may be an important factor.

Adolescent↗
PubMed2001

Partition controlled delivery of hydrophobic substances in toxicity tests using poly(dimethylsiloxane) (PDMS) films.

Interpretation of toxicity test results may be hampered when doubt exists about the actual exposure concentration. Processes that are responsible for differences between the nominal and the actual concentration in aqueous test systems may include sorption, precipitation, volatilization, chemical and biological degradation, and uptake into biological or test tissue. In this study, the use of a poly(dimethylsiloxane) (PDMS) film containing the test compound is introduced as a versatile technique for partition controlled delivery of hydrophobic compounds to aqueous toxicity tests. Two methods developed produced preloaded films, having toxicant added to the PDMS prepolymer solution before film deposition and curing, and postloaded films, which are created by the addition of toxicant in a solvent to an already-polymerized PDMS film. Preloaded films were generally more easily prepared, may better accommodate larger molecules, and have a higher capacity than postloaded films. Postloaded films provided film-solution partition coefficients with higher precision and allowed for the use of films from stock and thus for a more portable technique. Chemical analysis showed that equilibrium between films and the aqueous solution was established within 7-10 min and was maintained for a suite of aromatic compounds (log Kow ranging from 2.8 to 6.1). The reliability of the film technique was demonstrated by application to the Microtox bacterial toxicity tests of solutions of polycyclic aromatic hydrocarbons (PAHs).

Absorption↗