Temperature effect on physical and chemical properties of secondary organic aerosol from <i>m</i>-xylene photooxidation

The chemical and physical differences of secondary organic aerosol (SOA) formed at select isothermal temperatures (278 K, 300 K, and 313 K) are explored with respect to density, particle volatility, particle hygroscopicity, and elemental chemical composition. A transition point in SOA density, volatility, hygroscopicity and elemental composition is observed near 290–292 K as SOA within an environmental chamber is heated from 278 K to 313 K, indicating the presence of a thermally labile compound. No such transition points are observed for SOA produced at 313 K or 300 K and subsequently cooled to 278 K. The SOA formed at the lowest temperatures (278 K) is more than double the SOA formed at 313 K. SOA formed at 278 K is less hydrophilic and oxygenated while more volatile and dense than SOA formed at 300 K or 313 K. The properties of SOA formed at 300 K and 313 K when reduced to 278 K did not match the properties of SOA initially formed at 278 K. This study demonstrates that it is insufficient to utilize the enthalpy of vaporization when predicting SOA temperature dependence.

Temperature effect on physical and chemical properties of secondary organic aerosol from <i>m</i>-xylene photooxidation

The chemical and physical differences of secondary organic aerosol (SOA) formed at select isothermal temperatures (278 K, 300 K, and 313 K) are explored with respect to density, particle volatility, particle hygroscopicity, and elemental chemical composition. A transition point in SOA density, volatility, hygroscopicity and elemental composition is observed near 290–292 K as SOA within an environmental chamber is heated from 278 K to 313 K, indicating the presence of a thermally labile compound. No such transition points are observed for SOA produced at 313 K or 300 K and subsequently cooled to 278 K. The SOA formed at the lowest temperatures (278 K) is more than double the SOA formed at 313 K. SOA formed at 278 K is less hydrophilic and oxygenated while more volatile and dense than SOA formed at 300 K or 313 K. The properties of SOA formed at 300 K and 313 K when reduced to 278 K did not match the properties of SOA initially formed at 278 K. This study demonstrates that it is insufficient to utilize the enthalpy of vaporization when predicting SOA temperature dependence.

Relationship between Glycosyl Hydrolase Inventory and Growth Physiology of the Hyperthermophile Pyrococcus furiosus on Carbohydrate-Based Media

ABSTRACT Utilization of a range of carbohydrates for growth by the hyperthermophile Pyrococcus furiosus was investigated by examining the spectrum of glycosyl hydrolases produced by this microorganism and the thermal labilities of various saccharides. Previously, P. furiosus had been found to grow in batch cultures on several α-linked carbohydrates and cellobiose but not on glucose or other β-linked sugars. Although P. furiosuswas not able to grow on any nonglucan carbohydrate or any form of cellulose in this study (growth on oat spelt arabinoxylan was attributed to glucan contamination of this substrate), significant growth at 98°C occurred on β-1,3- and β-1,3–β-1,4-linked glucans. Oligosaccharides generated by digestion with a recombinant laminarinase derived from P. furiosus were the compounds that were most effective in stimulating growth of the microorganism. In several cases, periodic addition of β-glucan substrates to fed-batch cultures limited adverse thermochemical modifications of the carbohydrates (i.e., Maillard reactions and caramelization) and led to significant increases (as much as two- to threefold) in the cell yields. While glucose had only a marginally positive effect on growth in batch culture, the final cell densities nearly tripled when glucose was added by the fed-batch procedure. Nonenzymatic browning reactions were found to be significant at 98°C for saccharides with degrees of polymerization (DP) ranging from 1 to 6; glucose was the most labile compound on a mass basis and the least labile compound on a molar basis. This suggests that for DP of 2 or greater protection of the nonreducing monosaccharide component may be a factor in substrate availability. For P. furiosus, carbohydrate utilization patterns were found to reflect the distribution of the glycosyl hydrolases which are known to be produced by this microorganism.

REVERSIBLE N,O-HALOACYL SHIFT IN SERINE DERIVATIVES WITH ANTITUMOR ACTIVITY

Large doses of N-dichloroacetyl-DL-serine sodium salt were required to cause regression of Sarcoma-37 in mice. About 56% of the unchanged compound was recovered from the urine. These observations suggest that the antitumor activity may reside in a metabolic product of the N-dichloroacetyl serine. It is postulated that the active compound is the corresponding O-dichloroacetyl-DL-serine formed from the N-acyl compound by an in vivo enzymatically controlled shift which takes place via the hydroxyoxazolidine and (or) the oxazoline rings. O-Dichloroacetyl-DL-serine hydrochloride was prepared by treating a suspension of N-dichloroacetyl-DL-serine in anhydrous ether with gaseous hydrogen chloride. The free base, O-dichloroacetyl-DL-serine, is an extremely labile compound and reverts to the N-compound in neutral aqueous solution at room temperature. The hydrochloride salt, however, is stable, in which form it was isolated and characterized. The same compound was prepared from serine and dichloroacetic anhydride in dichloroacetic acid. O-Dichloroacetyl-DL-serine hydrochloride displays an antitumor effect against Sarcoma-37 and Sarcoma-180 in mice. The work has been extended to the monochloro- and trichloro-acetyl derivatives of serine.

THE BIOCHEMISTRY OF THE NITRIFYING ORGANISMS: PART 7. THE PHOSPHATE COMPOUNDS OF NITROBACTER AND THE UPTAKE OF ORTHOPHOSPHATE BY THE ORGANISM

The phosphate compounds present in the cells of the chemosynthetic autotrophic bacterium Nitrobacter were fractionated by means of successive extractions with cold 5% trichloracetic acid, ethanol, ethanol:ether, and dilute alkali. It was found that about 50% of the total cell phosphate was soluble in dilute alkali and, of this, 76% was acid-labile. Treatment of the alkali extract with Norit reduced the content of non-labile phosphate without affecting the acid-labile component; this labile compound was identified as a polyphosphate. By the use of 32P-labelled orthophosphate, it was shown that the cells absorbed orthophosphate from the medium at a slow rate during nitrite oxidation.

THE BIOCHEMISTRY OF THE NITRIFYING ORGANISMS: PART 7. THE PHOSPHATE COMPOUNDS OF NITROBACTER AND THE UPTAKE OF ORTHOPHOSPHATE BY THE ORGANISM

The phosphate compounds present in the cells of the chemosynthetic autotrophic bacterium Nitrobacter were fractionated by means of successive extractions with cold 5% trichloracetic acid, ethanol, ethanol:ether, and dilute alkali. It was found that about 50% of the total cell phosphate was soluble in dilute alkali and, of this, 76% was acid-labile. Treatment of the alkali extract with Norit reduced the content of non-labile phosphate without affecting the acid-labile component; this labile compound was identified as a polyphosphate. By the use of 32P-labelled orthophosphate, it was shown that the cells absorbed orthophosphate from the medium at a slow rate during nitrite oxidation.