Molecular orbital studies on brominated diphenyl ethers. Part I--conformational properties

Polybrominated diphenyl ethers (PBDEs) are widely used as additive flame retardants and quantities in the environment are on the rise. Because they are structurally related to polychlorinated biphenyls and also to thyroid hormones, there is serious concern that PBDEs may pose a danger to human health. Knowledge of their conformational properties is key to assessing their environmental fate and risk. The conformational properties of PBDEs were investigated by quantum chemical methods including semiempirical self-consistent field molecular orbital (SCF-MO), ab initio SCF-MO and density functional theory (DFT). Conformational analyses of model congeners 2,2',4,6'-tetrabromodiphenyl ether and 2,3,4,4',5,6-hexabromodiphenyl ether, based on energy maps calculated by semiempirical AM1 method, may indicate that all PBDE congeners except those with the tetra-ortho-bromination are conformationally flexible (or soft) due to low energy barriers for interconversion of stable conformers. The results of the conformational analyses are in conformity with recently published X-ray crystallographic data. For comparison with the results of the semiempirical method, higher level ab initio and DFT models were applied as well. The optimized geometries all lie well inside low energy regions on the maps and thus also ascertain the semiempirical calculations. According to computed geometric parameters and net atomic charges, the model B3LYP/3-21G* seemed to give better results than B3LYP/6-31G* and HF/6-31G*.     

Molecular orbital studies on brominated diphenyl ethers. Part II--reactivity and quantitative structure-activity (property) relationships

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants and are increasingly turning up in the environment. Their structural similarities to polychlorinated biphenyls and thyroid hormones suggest they may be a risk to human health. The present study examines the reactivity of brominated diphenyl ethers (BDEs) on the basis of the electronic structures as calculated by semiempirical AM1 self-consistent field molecular orbital (SCF-MO) method. Frontier orbital energies were used to elucidate the reactivity of BDEs in electrophilic, nucleophilic and photolytic reactions. From an examination of the frontier electron densities, the regioselectivity, or orientation, of metabolic reactions of BDEs was predicted. Furthermore, satisfactory quantitative structure-activity (property) relationship (QSAR and QSPR) models were derived to calculate gas chromatographic and ultraviolet spectral properties and luciferase induction activities from the AM1-computed electronic parameters.     

Sperm competition in the damselfly Enallagma hageni Walsh (Odonata: Coenagrionidae): benefits of multiple mating to males and females

Summary Sperm competition was investigated in the non-territorial damselfly, Enallagma hageni. Using irradiated (sterile) male techniques, the last male to mate was found to fertilize up to 95% of the eggs of the first clutch laid after mating. Dissection of females collected before, during, and after copula showed that a male removes a maximum of 87% of the sperm by volume of a previous mate. These data verify an earlier estimate of lifetime reproductive success in this species which was based on mating success, and suggest that indirect dissection methods offer minimum estimates of sperm precedence. Male E. hageni have ample opportunity to benefit from sperm precedence, since at least 10% of the receptive females encountered had already mated once that day, but still contained complete or partial clutches of eggs. Female E. hageni benefit directly from high sperm precedence because it allows them to exchange matings for guarding service by males during oviposition bouts under water.     

Change in spring arrival of migratory birds under an era of climate change,Swedish data from the last 140 years

Many migratory bird species have advanced their spring arrival during the latest decades, most probably due to climate change. However, studies on migratory phenology in the period before recent global warming are scarce. We have analyzed a historical dataset (1873–1917) of spring arrival to southern and central Sweden of 14 migratory bird species. In addition, we have used relative differences between historical and present-day observations (1984–2013) to evaluate the effect of latitude and migratory strategy on day of arrival over time. There was a larger change in spring phenology in short-distance migrants than in long-distance migrants. Interestingly, the results further suggest that climate change has affected the phenology of short-distance migrants more in southern than in central Sweden. The results suggest that the much earlier calculated arrival to southern Sweden among short-distance migrants mirrors a change in location of wintering areas, hence, connecting migration phenology and wintering range shifts.     

Evaluation of a tape-stripping technique for measuring dermal exposure to pyrene and benzo(a)pyrene

Epidemiological studies have shown an increased incidence of cancer among workers occupationally exposed to polycyclic aromatic hydrocarbons (PAHs). As the dermal route is considered important for exposure to PAHs in the workplace, the aim of this study was to develop and evaluate a tape-stripping technique for monitoring dermal exposure to pyrene and benzo(a)pyrene. The tape-stripping method was evaluated by applying different concentrations of pyrene and benzo(a)pyrene directly onto tape strips (spiked tapes), clean glass plates, and on the skin of five volunteers. The glass plates were stripped using a single strip of tape and the skin of the volunteers was stripped with five consecutive strips of tape after 0 and 30 minutes. The method was also tested on five chimney sweeps at three exposure sites. High-performance liquid chromatography with fluorescence detection was employed for the quantification of pyrene and benzo(a)pyrene. The mean recovery from the spiked tapes was 97% for pyrene and 93% for benzo(a)pyrene. The mean overall recovery from the glass plates was 88% and 76% for pyrene and 88 and 85% for benzo(a)pyrene. The recovery from human skin was 70% and 63% for pyrene and 60 and 54% for benzo(a)pyrene, after 0 and 30 minutes, respectively. A concentration gradient was clearly detected between the five consecutive strips. Detectable amounts of pyrene and benzo(a)pyrene were found on all chimney sweeps at all exposure sites. This method can thus be used to detect and quantify dermal exposure to pyrene and benzo(a)pyrene. The results also show that pyrene and benzo(a)pyrene may be taken up by the skin.     

Tests of the harassment-reduction function and frequency-dependent maintenance of a female-specific color polymorphism in a damselfly

Color polymorphisms have provided classical examples of how frequency-dependent selection maintains genetic variation in natural populations. Here we tested for the first time, the hypothesized adaptive function of a female-specific color polymorphism in odonates to lower male harassment towards females generally. Under conditions controlling for sex ratio, population density and morph frequency, we also tested two major frequency-dependent selection hypotheses for the maintenance of the polymorphism. Using groups of captive Enallagma hageni, whose females are either green or a male-like blue, we varied morph frequency at two sex ratios. We quantified sexual harassment towards females by visual observations, and by the presence of dust on females that was transferred from dusted males. Per capita harassment rate for the female-monomorphic treatments did not differ from that of the female-polymorphic treatments. At a male-biased sex ratio, per capita harassment rate towards blue, but not green females increased with morph frequency, providing partial support for frequency-dependent selection resulting from male learning of female morphs. Even at high frequency, green females were not harassed more than blue, contrary to the prediction that males should always recognize green females as mates. Moreover, frequency-dependent harassment towards blue females was not detectable using harassment measured with dust evidence, which greatly underestimated the incidence of sexual harassment. Our findings identified problems with the use of insectaries and the dusting technique to quantify male sexual harassment towards females, as well as with a past insectary experiment on Ischnura elegans that failed to demonstrate frequency-dependent harassment.     

持久性有机污染物(POPs)的监测:来自瑞典韦特恩湖的例子

位于瑞典南部的韦特恩湖是一个大的贫营养化湖泊,它具有高的水面与流域面积比率(大约为0.4)和60年的驻水时间.此湖结合了对大气POP污染的敏感性、对POPs影响的普通敏感性和较慢的浓度降低.提出了鱼体内PCBs和DDT从20世纪60年代一直到1996年的时间系列,以及韦特恩湖沉积物中TCDD的数据,并和其它大湖泊进行了比较.有关北极红点鲑(Salvelinus salvelinus)体内POPs的长期数据集显示每年PCBs有大约5%,DDT有13%的减少.这些速度和其它研究相一致.也讨论了营养物质及其生物效应,以及影响具有长驻水时间的贫营养化湖泊命运的因素.我们提出贫营养的干净湖泊是对于监测生物区中POPs的重要生态系统.     

Lifetime mating success in a natural population of the damselfly,Enallagma hageni (Walsh) (Odonata: Coenagrionidae)

Summary Variance in lifetime mating success was measured for individuals of a population of Enallagma hageni, a non-territorial damselfly in northern Michigan. E. hageni is an explosive breeder with scramble competition for mates. Highly skewed operational sex ratios resulted in intense male-male competition which took the form of interference with tandem pairs. 41% of the males failed to mate in their lifetime as opposed to only 3.6% mating failure in females. The effect on mating success of size, age, longevity, and time spent at the breeding site were investigated. Intermediate sized males obtained the most matings, and male lifetime mating success was highly correlated with longevity.     

Radiosynthesis of perfluorooctanesulfonate (PFOS) and perfluorobutanesulfonate (PFBS), including solubility, partition and adhesion studies

Here, we describe for the first time the synthesis of [³⁵S] PFOS and [³⁵S] PFBS with sulfur-35 enriched sulfur dioxide as the radiolabelled reagent, resulting in 2.5 and 2.3 mCi of product, respectively. Basic information concerning the physicochemical properties of perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate (PFBS) and perfluorooctanoic acid (PFOA) are still limited. Hence, we utilized these radiolabelled perfluoroalkanesulfonates (PFSAs), as well as carbon-14 labelled perfluorooctanoic acid ([¹⁴C] PFOA) to determine some basic characteristics of physiological and experimental significance.The solubility of PFOS in buffered aqueous solutions at pH 7.4 was found to be severely reduced in the presence of potassium and sodium ions, which, however, did not reduce the solubility of PFOA or PFBS. PFOS was found to adhere to a small extent to polypropylene and polystyrene, whereas no such adhesion of PFOA or PFBS was detected. The extents of adhesion of PFOS and PFOA to glass were found to be 20% and 10%, respectively. For the first time, the partition coefficients for PFOS, PFBS and PFOA between n-octanol and water were determined experimentally, to be −0.7, −0.3, and 1.4, respectively, reflecting the difference in the amphiphilic natures of these molecules.