Total Number Of Carbon Atoms Research Articles

Three-dimensional enhanced lipidomics analysis combining UPLC, differential ion mobility spectrometry, and mass spectrometric separation strategies

Phospholipids serve as central structural components in cellular membranes and as potent mediators in numerous signaling pathways. There are six main classes of naturally occurring phospholipids distinguished by their distinct polar head groups that contain many unique molecular species with distinct fatty acid composition. Phospholipid molecular species are often expressed as isobaric species that are denoted by the phospholipid class and the total number of carbon atoms and double bonds contained in the esterified fatty acyl groups (e.g., phosphatidylcholine 34:2). Techniques to separate these molecules exist, and each has positive and negative attributes. Hydrophilic interaction liquid chromatography uses polar bonded silica to separate lipids by polar head group but not by specific molecular species. Reversed phase (RP) chromatography can separate by fatty acyl chain composition but not by polar head group. Herein we describe a new strategy called differential ion mobility spectrometry (DMS), which separates phospholipid classes by their polar head group. Combining DMS with current LC methods enhances phospholipid separation by increasing resolution, specificity, and signal-to-noise ratio. Additional application of specialized information-dependent acquisition methodologies along with RP chromatography allows full isobaric resolution, identification, and compositional characterization of specific phospholipids at the molecular level.

Aggregation morphologies of a series of heterogemini surfactants with a hydroxyl head group in aqueous solution.

The aggregation behaviors of a series of heterogemini surfactants N,N-dimethyl-N-[3-(alkyloxy)-2-hydroxypropyl]-alkylammonium bromide, abbreviated as CmOhpNCn (m, n = 10, 8; 10, 14; 12, 8; 12, 10; 12, 12; 12, 14; 14, 8 and 14, 10), have been investigated in aqueous solution. Electric conductivity, steady-state and frequency sweep rheological measurements were adopted to study the micellar morphology affected by molecular structure, concentration and temperature, and a close relationship among them was established. Electric conductivity measurement results indicated that Krafft temperatures were mainly related to the total number of carbon atoms, while the CMC values were affected by the combined factors of alkyl chain length, degree of dissymmetry and hydroxyl head group. And some unusual values may come from the poor water solubility induced by the relatively long alkyl chain n. Dynamic rheological results and cryo-TEM images revealed various micellar behaviors of CmOhpNC8 affected by different combined factors. When m value was increased, the formation of quite long rodlike or wormlike micelles derived from the enhanced hydrophobility and hydrogen bonding. And the effect of concentration on aggregation behavior was similar to that of m value except for formation of micellar joints. With temperature increase, the decreased viscosity of C14OhpNC8 was due to formation of micellar joints and weakening of hydrogen bonding, which could be confirmed by dynamic light scattering (DLS). Furthermore, the C14OhpNC8 aggregates formed below the Krafft temperature were more likely to be affected by temperature at high concentrations.

Structure and aggregation in the 1,3-dialkyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquid family: 2. From single to double long alkyl side chains.

A systematic molecular dynamics study using large simulation boxes has been performed in order to extend the analysis of the mesoscopic segregation behavior observed in ionic liquids of the 1,3-dialkyl-imidazolium bis(trifluoromethylsulfonyl)imide homologous series, [C(n)C(mim)][Ntf2] (2 ≤ n ≤ 10, 2 ≤ m ≤ n). The analyses include the discussion of the structure factors, S(q), in the low-q range (1.6 ≤ q/nm(-1) ≤ 20); the confirmation of the periodicity of the polar network of the ionic liquid and its relation to the so-called intermediate peaks; and the characterization of the polar network and the nonpolar regions that are formed along the series using aggregate analyses by means of five different statistical tools. The analyses confirmed that the percolation of the nonpolar regions into a continuous domain occurs when the total number of carbon atoms in the alkyl chains exceeds six but that this is not a sufficient condition for the emergence of a distinct and intense prepeak. The existence of such a peak also requires that the longer alkyl chain contains more than a critical alkyl length (CAL) of five carbon atoms.

Ethylene‐bridged Periodic Mesoporous Organosilicas with Large Spherical Pores Templated by PEO‐PPO‐PEO Surfactant Micelles Swollen by Ethylbenzene

AbstractThe applicability of a recently identified potent micelle swelling agent, ethylbenzene, was verified for periodic mesoporous organosilicas (PMOs) and its performance was found to be comparable to that of xylene, which was previously shown to be an excellent swelling agent for surfactant‐templated ordered mesoporous silica and organosilica synthesis. Large‐pore ethylene‐bridged PMOs with face‐centered cubic structures of spherical mesopores were synthesized using Pluronic F127 (EO106PO70EO106) surfactant and ethylbenzene or xylene swelling agents at temperatures from 15 down to 7 °C. In the case of ethylbenzene, PMOs were synthesized at 15 °C using two different amounts of the inorganic salt (KCl) and under salt‐free conditions. It was found that ethylbenzene and xylene perform comparably well, allowing one to synthesize highly ordered face‐centered cubic ethylene‐bridged PMOs with unit‐cell parameters ca. 40 nm and nominal pore diameters ca. 14 nm. It was also possible to convert PMO prepared in the presence of ethylbenzene to silica with nearly closed mesopores via calcinations at 400 °C under air. The dependence of the PMO structure on the initial synthesis temperature and the salt concentration was found to be highly similar for ethylbenzene and xylene. Because of the fact that xylene (dimethylbenzene) was found earlier to work differently from toluene (methylbenzene) and trimethylbenzene, the observed similarity between the performance of xylene and ethylbenzene confirms an expectation that the suitability of alkylbenzenes for PEO‐PPO‐PEO block‐copolymer‐templated synthesis of well‐defined porous materials depends primarily on the total number of carbon atoms in their alkyl substituents. This finding is expected to streamline the process of identifying effective swelling agents for PMOs and other mesoporous materials.

How aliphatic alcohols and pH affect reactivity of horse blood serum cholinesterase at its interaction with organophosphorus inhibitors

There was studied action of aliphatic alcohols (ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol), and pH on various kinds of serum cholinesterase. At inhibition of the cholinesterase hydrolytic activity under effect of alcohols the key role was played not by the total number of carbon atoms in the alcohol molecule, but by the “efficient length” of the carbohydrate chain. The fact that the presence of alcohols did not affect parameters of reversible inhibition of cholinesterase by onium ions tetramethylammonium and choline allows suggesting the absence of action of solvents on specific sorption of acetylcholine in the enzyme active center. With aid of two sets of hydrophobic organophosphorus inhibitors (OPI) (12 compounds), we have managed to estimate both the degree and the character itself of serum cholinesterase.

Library Synthesis and Antibacterial Investigation of Cationic Anthraquinone Analogs

We report the parallel synthesis of a series of novel 4,9-dioxo-4,9-dihydro-1H-naphtho[2,3-d][1,2,3]triazol-3-ium chloride salts, which are analogs to cationic anthraquinones. Three synthetic protocols were examined leading to a convenient and facile library synthesis of the cationic anthraquinone analogs that contain double alkyl chains of various lengths (C(2)-C(12)) at N-1 and N-3 positions. The antibacterial activities of these compounds were evaluated against Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli. The antibacterial activities of these compounds were expected to be associated with the structural features of naphthoquinone, cation and lypophilic alkyl chain and, interestingly, they showed much higher levels of antibacterial activities against G+ than G- bacteria. In addition, when the total number of carbon atoms of the alkyl groups at both N-1 and N-3 positions lies between 9 and 18, the bactericidal activity against S. aureus increased with increasing alkyl chain length at both N-atoms with MIC ≤ 1 μg/mL.

Widening or Lengthening? Enhancing the First Hyperpolarizability of Tubiform Multilithium Salts

Very recently, tubiform multilithium salts have been investigated as new candidates for high-performance nonlinear optical (NLO) materials because of their large static first hyperpolarizability (β0) (J. Phys. Chem. C 2009, 113, 4984−4986). The interesting question of how to further enhance the β0 value of the multilithium salt, by widening or lengthening the tubiform cyclacene, is studied in this work. On one hand, the effect of widening on the β0 value of tubiform multilithium salts is investigated using Lin-[n]cyclacene (n = 5–8). We found that the β0 value (15497 au) of Li8-[8]cyclacene is 3 times larger than the 5028 au value of the Li5-[5]cyclacene, with the total number of carbon atoms increasing from 20 to 32. On the other hand, lengthening Li5-[5]cyclacene to form Li5–CNT (5,0) results in the dramatically enhanced β0 value of 146642 au, which is 29 times larger than the value for the Li5-[5]cyclacene, even though the total number of carbon atoms is increased only from 20 to 30. Further, the secon...

Pyrogallol[4]arenes Show Highly Variable Amphiphilic Behavior at the Air–Water Interface Dependent Upon Side Chain Length and Branching

The behavior of pyrogallol[4]arenes (Pgs) substituted with normal and branched alkyl side chains at the air-water interface was examined on a Langmuir trough. The amphiphilic systems studied form stable monolayers when the straight chains are as short as n-propyl. Remarkably, n-propylpyrogallol[4]arene shows a behavior at the air-water interface that is indistinguishable from that of pyrogallolarenes bearing n-hexyl, n-nonyl, and n-dodecyl side chains. There is no report of amphiphilic side-chain-length dependence or Langmuir trough behavior for families of branched alkyl chain calixarenes or resorcinarenes. In the Pg family reported here, Pgs with straight chains (except for methyl and ethyl) behave very similarly to each other and very differently from symmetrical branched chain analogues having the same total number of carbon atoms. For example, the shortest possible branched side chain of a Pg, isopropyl-Pg, forms stable monolayers by a unique molecular subduction mechanism. Isopropyl-Pg (dimethylmethyl side chain, iPrPg) and 3-pentyl-Pg (diethylmethyl side chain, 3-pentylPg) both show high levels of organization, albeit by quite different mechanisms, at the air-water interface. Both iPrPg and 3-pentylPg differ in behavior from 4-heptylPg. Brewster angle microscopy revealed differences in organization of the Pgs that supports the mechanistic suggestions offered herein.

Inter-relationships between solubilities, distribution coefficients and melting points of some substituted benzoic and phenylacetic acids.

Ten 4-hydroxy and 4-alkoxy benzoic and phenylalkanoic acids have been investigated. Solubilities in aqueous buffer at pH 1.2 were determined, together with distribution coefficients between the buffer and either octanol or isopropyl myristate. When plotted against the total number of carbon atoms in the side chains, log octanol/water distribution coefficients gave two parallel straight lines, one for the substituted benzoic acids, and the other for the substituted phenylalkanoic acids. The slopes approximated to 0.5, the generally accepted value for methylene. Similar plots could be obtained with isopropyl myristate, provided the hydroxy acid results were ignored, and also when log aqueous solubilities were plotted against carbon number, although there was considerable scatter. The differences between the distribution coefficient results were explained in terms of solute-solvent interactions, and the scatter attributed to variations in the heats of fusion of the solutes. Yalkowsky's equation (1977), linking aqueous solubilities and melting points with distribution coefficients, was applied to the results, and found to be of limited predictive value.

Comprehensive analysis of the major lipid classes in sebum by rapid resolution high-performance liquid chromatography and electrospray mass spectrometry

Sebum is a complex lipid mixture that is synthesized in sebaceous glands and excreted on the skin surface. The purpose of this study was the comprehensive detection of the intact lipids that compose sebum. These lipids exist as a broad range of chemical structures and concentrations. Sebum was collected with SebuTape(TM) from the foreheads of healthy donors, and then separated by HPLC on a C8 stationary phase with sub 2 µm particle size. This HPLC method provided high resolution and excellent reproducibility of retention times (RT). Compound mining was performed with time of flight (TOF) and triple quadrupole (QqQ) mass spectrometers (MS), which allowed for the classification of lipids according to their elemental composition, degree of unsaturation, and MS/MS fragmentation. The combination of the two MS systems detected 95 and 29 families of triacylglycerols (TAG) and diacylglycerols (DAG), respectively. Assignment was carried out regardless of positional isomerism. Among the wax esters (WE), 28 species were found to contain the 16:1 fatty acyl moiety. This method was suitable for the simultaneous detection of squalene and its oxygenated derivative. A total of 9 cholesterol esters (CE) were identified and more than 48 free fatty acids (FFA) were detected in normal sebum. The relative abundance of each individual lipid within its own chemical class was determined for 12 healthy donors. In summary, this method provided the first characterization of the features and distribution of intact components of the sebum lipidome.

One-pot synthesis and characterization of Fe II–Fe III hydroxide (green rust) intercalated with C9–C14 linear alkyl carboxylates

Layered Fe II–Fe III hydroxides (green rusts, GR) intercalated with monovalent aliphatic carboxylate anions, called GR-carboxylates, possess hydrophobic interlayer regions which can adsorb non-polar organic compounds. GRs are well known reductants and hence GR-carboxylates may have the potential to detoxify adsorbed compounds, such as chlorinated solvents. GR-carboxylates, GR CX, for the first time, were precipitated directly by aerial oxidation of an ethanolic solution containing FeSO 4 and linear alkyl carboxylate ions synthesis condition using monovalent carboxylic acids with X, the total number of carbon atoms in the acid, varying from 5 (pentanoic acid) to 14 (tetradecanoic acid), synthesis conditions were tested. GR CX formed for X ≥ 9. The syntheses were carried out at constant pH of 8 using 1 M NaOH as neutralizing agent, and with a maximum duration of 3.5 h. The basal spacings of GR CX increased with X and they were 2.68 nm (GR C9), 2.94 nm (GR C10), 3.59 nm (GR C12) and 4.16 nm (GR C14). The Mössbauer spectra measured at 80 K of different GR C12 synthesized under identical chemical conditions resulted in hyperfine parameters close to those of other GRs. The Fe II/Fe III ratios of the final products ( R) ranged between 1.4 and 2.8 demonstrating that Fe II in GR CX can be partly oxidized without degradation of the structure. R at various stages of the synthesis decreased from 5.2 at the start of the reaction to 2.8 at the end of synthesis. In the specific case of GR C12, the optimum initial solution concentrations were [C12] 0 = 25 mM, [Fe II] 0 = 30 mM and 40% (v/v) EtOH/H 2O.

Quantification of carbon contamination under electron beam irradiation in a scanning transmission electron microscope and its suppression by plasma cleaning

We have measured the build-up of carbon surface contamination as a function of time and irradiated area size for various specimens in a JEOL 2010F (scanning) transmission electron microscope, employing both t/λ mapping with our Gatan imaging filter and recording changes in annular dark-field image intensity. It is shown that the total number of carbon atoms deposited per time for a given beam intensity is roughly constant at room temperature for as-received specimens while it is significantly lower for plasma cleaned specimens. This explains why contamination is generally only an issue at the highest magnifications where the contamination regions become smaller and the carbon layers correspondingly thicker. A Fischione plasma cleaner was then used to remove these carbon layers, and the rate of carbon removal has been determined for contamination spots produced in stationary spot mode as well as for extended regions scanned for a minute so that optimal cleaning times can be chosen.

Spatial and temporal alterations of phospholipids determined by mass spectrometry during mouse embryo implantation

Molecular events involved in successful embryo implantation are not well understood. In this study, we used MALDI imaging mass spectrometry (IMS) technologies to characterize the spatial and temporal distribution of phospholipid species associated with mouse embryo implantation. Molecular images showing phospholipid distribution within implantation sites changed markedly between distinct cellular areas during days 4-8 of pregnancy. For example, by day 8, linoleate- and docosahexaenoate-containing phospholipids localized to regions destined to undergo cell death, whereas oleate-containing phospholipids localized to angiogenic regions. Arachidonate-containing phospholipids showed different segregation patterns depending on the lipid class, revealing a strong correlation of phosphatidylethanolamines and phosphatidylinositols with cytosolic phospholipase A(2alpha) and cyclooxygenase-2 during embryo implantation. LC-ESI-MS/MS was used to validate MALDI IMS phospholipid distribution patterns. Overall, molecular images revealed the dynamic complexity of lipid distributions in early pregnancy, signifying the importance of complex interplay of lipid molecules in uterine biology and implantation.

Average molecular structures of asphaltenes from vacuum residues of Venezuelan crudes: Theoretical study of thermodynamic properties

From experimental data of five residues of Venezuelan crudes, standard criteria of molecular characterization, molecular modeling and quantum semi-empirical calculations, a set of average molecular structures are proposed for their corresponding asphaltenes. The geometries of the proposed molecules were compared with structures of different asphaltene origins reported in the literature, where significant similarities and differences are observed for some cases. However, the molecular weights, H/C ratio, the number of aromatic and aliphatic carbons and the number of-CH3,-CH2-, CH- aliphatic groups of the average structures of the hypothetical asphaltenes, proposed in this work, agree satisfactorily with experimental values of very well know models. To rationalize the similarities and differences between the proposed asphaltenes and those of the literature, a theoretical study at semi-empiric level of the structures, energetic and thermodynamic properties was performed using the PM3 and PM6 parameterizations as implemented in MOPAC 09 software. As criteria for the stability of the asphaltenes, calculations were carried out for the heats of formation and the associated thermodynamic properties within 200 to 900 K temperature range. At 298.15 K, the results show that for the extended asphaltene structures the formation heat are underestimated at PM3 level, while the PM6 parametrization lead to values of this property that are consistent with the expected values according to the size, molecular composition and chemical nature of the studied structures. By other hand, it was determined that there are exist significant linear correlations between calculated thermodynamic parameters and variables that depend on the intrinsic structure of asphaltenes, such as molecular weight, total number of carbon atoms and total number of aromatic rings.

Methyl-branched poly(hydroxyalkanoate) biosynthesis from 13-methyltetradecanoic acid and mixed isostearic acid isomer substrates

Pseudomonas resinovorans, a known medium-chain-length (mcl-) poly(hydroxyalkanoate) (PHA) producer, was grown on 13-methyltetradecanoic acid (13-MTDA) and a mixture of isostearic acid (IA) isomers to produce methyl-branched mcl-PHA polymers. Shake-flask experiments revealed polymer productivities (the percent of the cell mass that is polymer) of 31 +/- 1% (n = 3) and 23 +/- 3% (n = 3) when grown in 13-MTDA and IA, respectively. Monomer content was determined by a combination of gas chromatography/mass spectrometry (GC/MS) of the acid hydrolyzed, silylated methyl esters, and nuclear magnetic resonance spectroscopy. Results showed that the mcl-PHA polymer derived from 13-MTDA was primarily composed of 3-hydroxy-7-methyloctanoic acid and 3-hydroxy-9-methyldecanoic acid (67 and 16 mol% by GC/MS, respectively). In contrast, the mcl-polymers synthesized from the IA isomeric mixture were more complex, containing both even and odd chain-length monomers as well as varying distributions of methyl-branched derivatives. The PHA distributions among the C8, C10, C12, and C14 carbon chain-length monomers included three isomers of C8, five isomers of C10, seven isomers of C12, and nine isomers of C14 each containing one linear-chain derivative and n-6 methyl-branched derivatives where n equals the total number of carbon atoms in each monomer unit (C8-C14).

Hydrophobic Moiety of Cationic Lipids Strongly Modulates Their Transfection Activity

Synthetic cationic lipids are widely used components of nonviral gene carriers, and the factors regulating their transfection efficiency are the subject of considerable interest. In view of the important role that electrostatic interactions with the polyanionic nucleic acids play in formation of lipoplexes, a common empirical approach to improving transfection has been the synthesis and testing of amphiphiles with new versions of positively charged polar groups, while much less attention has been given to the role of the hydrophobic lipid moieties. On the basis of data for approximately 20 cationic phosphatidylcholine (PC) derivatives, here we demonstrate that hydrocarbon chain variations of these lipids modulate by over 2 orders of magnitude their transfection efficiency. The observed molecular structure-activity relationship manifests in well-expressed dependences of activity on two important molecular characteristics, chain unsaturation and total number of carbon atoms in the lipid chains, which is representative of the lipid hydrophobic volume and hydrophilic-lipophilic ratio. Transfection increases with decrease of chain length and increase of chain unsaturation. Maximum transfection was found for cationic PCs with monounsaturated 14:1 chains. It is of particular importance that the high-transfection lipids strongly promote cubic phase formation in zwitterionic membrane phosphatidylethanolamine (PE). These remarkable correlations point to an alternative, chain-dependent process in transfection, not related to the electrostatic cationic-anionic lipid interactions.

Comparison of Surface‐Active Properties of (Alkyloxycarbonylmethyl)trimethylammonium Chlorides and Alkyltrimethylammonium Chlorides

AbstractSurface‐active properties of cleavable surfactants with a betaine ester group—(n‐alkyloxycarbonylmethyl)trimethylammonium chlorides, used as separation reagents—were investigated. Critical micelle concentrations, dispersing powers, and foaming powers were comparable to those of alkyltrimethylammonium chlorides with the same total number of carbon atoms. On the other hand, the solubilities of the four hydrophobic dyes N,N‐dimethyl‐3‐nitroaniline, naphthalene, pyrene, and oil orange SS in the former surfactant solutions were equal to or slightly smaller than those in the solutions of the latter surfactants with the same alkyl chain length. The alkali hydrolysis yields of the formers approached 100% in aqueous buffer solution at pH 10 and 25 °C within 10 min, and the yield at pH 9 was dependent on the alkyl chain length. This type of surfactant was also found to be as an efficient separation reagent which disperses carbon black and solubilizes the above dyes into aqueous neutral solution and then separates them instantaneously and almost perfectly as precipitates when a small excess of NaOH is added.

Directly resistively heated‐column gas chromatography for the evaluation of cow milk fat purity

AbstractCow milk fat purity is currently evaluated by triacylglycerol (TAG) analysis. The method is based on the gas chromatographic analysis of TAG according to their total number of carbon atoms, followed by the application of formulae deriving from multiple linear regressions. The original procedure was set up by using a packed column, but different successive works showed its suitability also with the adoption of more modern adjustments. Recently, the use of high‐speed gas chromatography has been spreading. In this work, the suitability of the directly resistively heated‐column gas chromatography [Ultrafast module (UFM)‐GC] for the evaluation of milk fat purity by the Official EU method was tested. Pure milk fat, together with mixtures of milk fat containing two levels of four foreign fats (coconut fat, sunflower oil, lard and beef tallow), were analyzed by both the conventional capillary GC method and UFM‐GC. Sheep, goat and buffalo milk fats were also analyzed. The reference material CRM‐519 was used for calibration. Repeatability and reproducibility values were always below the limits reported in the Official method, demonstrating the suitability of UFM‐GC for the evaluation of milk fat purity. The investigation on sheep, goat and buffalo milk fat confirmed that the S ranges, calculated for cow milk fat, are not applicable to the evaluation of genuineness of non‐bovine milk fats.

Molecular Simulation of the Effect of Temperature and Architecture on Polyethylene Barrier Properties

We present a multiscale approach for calculating the low-concentration solubility, diffusivity, and selectivity of small molecules through polymer matrixes. The proposed modeling scheme consists of two main stages; first, thoroughly equilibrated and representative poly(ethylene) (PE) atomistic melt configurations were obtained through the application of a Monte Carlo (MC) scheme based on advanced chain-connectivity altering moves (linear architectures) or the combination of localized MC moves followed by molecular dynamics. In the second phase, transition-state theory (TST), as proposed by Gusev and Suter [Gusev, A. A.; Suter, U. W. J. Chem. Phys. 1993, 99, 2228], was invoked in a coarser level of description to calculate the barrier properties of the studied macromolecules to small gas molecules at infinite dilution. The multiscale methodology was successfully applied on PE melts characterized by various molecular weights (MW) (from C78 up to C1000) and polydispersity indices at a wide range of temperature conditions. The effect of molecular architecture on the barrier properties was examined through the comparison between linear and short-chain branched structures bearing the same total number of carbon atoms. Simulation results were found to be in very good agreement with available experimental data. Additionally, the new scheme has been further validated by comparing the qualitative behavior of solubility, diffusivity, and selectivity with previously reported trends in the literature based on both experimental and simulation studies. The present study concludes that density plays a dominant role that determines the behavior of the polymer as a barrier material, especially in terms of diffusivity. Additionally, it is evidenced that short-chain branching has a small effect on the barrier properties of PE when the comparison is performed on purely amorphous samples. The hierarchical method presented here not only is faster when compared against conventional molecular dynamics simulations, but in some cases, like the vicinity of the glass transition temperature or for long polymer chain melts, it opens the way to the calculation of the barrier properties at realistic simulation times.

Absolute electron impact ionization cross-sections and polarisability volumes for C 2 to C 4 aldehydes, C 4 and C 6 symmetric ethers and C 3 to C 6 ketones

Absolute total electron impact ionization cross-sections from 15 to 285 eV are reported for the C 2 to C 4 aldehydes, the C 2 v symmetric C 4 and C 6 ethers and C 3 to C 6 ketones. The reproducibility of the measured cross-sections over the full energy range is better than ±4%, and absolute cross-sections measured for N 2 and SF 6 as reference species are in excellent agreement with values reported by several other groups claiming accuracies of around ±5%. Monotonic relationships previously shown to exist between maximum ionization cross-section and polarisability volume and between maximum ionization cross-section and the total number of carbon atoms in the skeletal chain are shown to apply to the aldehydes, ethers and ketones reported here. These relationships provide useful means for estimating unknown cross-sections with available literature polarisability volumes in good accord with values estimated from the measured maximum ionization cross-sections. The experimental data were also compared with calculations carried out using the binary encounter Bethe (BEB) method for the calculation of total ionization cross-sections.