How diversification rates and diversity limits combine to create large-scale species-area relationships

Species-area relationships (SARs) have mostly been treated from an ecological perspective, focusing on immigration, local extinction and resource-based limits to species coexistence. However, a full understanding across large regions is impossible without also considering speciation and global extinction. Rates of both speciation and extinction are known to be strongly affected by area and thus should contribute to spatial patterns of diversity. Here, we explore how variation in diversification rates and ecologically mediated diversity limits among regions of different sizes can result in the formation of SARs. We explain how this area-related variation in diversification can be caused by either the direct effects of area or the effects of factors that are highly correlated with area, such as habitat diversity and population size. We also review environmental, clade-specific and historical factors that affect diversification and diversity limits but are not highly correlated with region area, and thus are likely to cause scatter in observed SARs. We present new analyses using data on the distributions, ages and traits of mammalian species to illustrate these mechanisms; in doing so we provide an integrated perspective on the evolutionary processes shaping SARs.     

Iron-mediated free-radical formation of signaling lipids in a model system

It has been shown using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and its combination with thin-layer chromatography (TLC) that the action of the ascorbate/Fe(2+)/H(2)O(2) oxidizing system on cardiolipin and galactocerebroside results in the formation of phosphatidic acid (PA) and ceramide (Cer), respectively. These data, when combined with results obtained on radiolysis of similar substances, allowed the conclusion that the formation of PA and Cer occurs via an OH-induced fragmentation taking place in polar moiety of the starting substrates.     

Radiation-induced free-radical transformation of phospholipids: MALDI-TOF MS study

Under the action of free-radical reaction initiators on membrane phospholipids, complex processes are taking place in both hydrophobic and hydrophilic parts of the phospholipids. Realization of these processes results in a mixture consisting of the initial lipids and their peroxidation and fragmentation products. Identification of compounds in such mixtures requires analytical methods of high sensitivity, reproducibility and accuracy to be applied. These properties are characteristic of the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method. In the studies of radiation-induced free-radical transformations of phosphatidylglycerol, the MALDI-TOF MS in combination with thin layer chromatography (TLC) has been shown to be able to detect and identify products of free-radical transformations taking place in both hydrophilic and hydrophobic parts of the phospholipid. Thus, the MALDI-TOF MS can serve as a suitable analytical tool to investigate free-radical transformations of lipids.     

Effects of vitamins, coenzymes and amino acids on reactions of homolytic cleavage of the O-glycoside bond in carbohydrates

It has been established that vitamins B1, K3 and C, coenzyme Q0 and amino acids cysteine and histidine effectively inhibit reactions of homolytic cleavage of the O-glycoside bond, which are responsible for the destruction of di- and polysaccharides on gamma-irradiation or the action of other reactive radical initiators. This effect was shown to originate from either oxidation or reduction of the radicals of carbohydrates undergoing destruction.     

Formation of phosphatidic acid, ceramide, and diglyceride on radiolysis of lipids: identification by MALDI-TOF mass spectrometry

By use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, phosphatidic acid was found to be the main product of γ radiolysis of cardiolipin, phosphatidylinositol, and phosphatidylglycerol. It has been shown that γ irradiation of such glycolipids as cerebroside and galactosyl diglyceride leads to formation of ceramide and diglyceride, respectively. These findings, combined with those obtained earlier, allowed an assumption to be made that, owing to radiation-induced free radical fragmentation of lipids in their polar moiety, formation of signaling molecules can occur.     

Novel (3,5-di-tert-butyl-2-hydroxy-phenylcarbamoyl)-alkanoic acids as potent antioxidants

A series of novel phenolic antioxidants of amphiphilic structure has been synthesized. Investigations into the influence of aliphatic spacer length and nature of a hydrophilic anchor on the antioxidant activity allowed elucidating certain structure requirements for the membrane-addressed antioxidant designing.     

Influence of Ethanol and Phosphatidylethanol on the Activity of Pancreatic Phospholipase A2

Hydrolysis of dioleoylphosphatidylethanol (DOPEt) and dioleoylphosphatidylcholine (DOPC) catalyzed by phospholipase A₂ (PLA₂) from porcine pancreas has been studied in single-component and binary liposomes in the absence and in the presence of ethanol. DOPEt (an anionic phospholipid) was found to increase the rate of hydrolysis of zwitterionic DOPC in liposomes under the action of PLA₂.     

1-Acyl-2-[N-(2,4-dinitrophenyl)aminopropionyl]-sn-glycero-3-phosphocholine as a chromogenic substrate for phospholipase A2 assay

We have developed a spectrophotometric assay for phospholipase A₂ activity using 2,4-dinitrophenyl-labeled phosphatidylcholine as substrate. The assay allows quite simple quantification of phospholipase A₂ activity by measuring the absorbance of the aqueous phase after extraction of the reaction mixture and requires neither chromatographic separation of the reaction products nor the addition of auxiliary coloring reagents.     

1-Acyl-2-[N-(2,4-dinitrophenyl)aminopropionyl]-sn-glycero-3-phosphocholine as a chromogenic substrate for phospholipase A₂ assay

We have developed a spectrophotometric assay for phospholipase A(2) activity using 2,4-dinitrophenyl-labeled phosphatidylcholine as substrate. The assay allows quite simple quantification of phospholipase A(2) activity by measuring the absorbance of the aqueous phase after extraction of the reaction mixture and requires neither chromatographic separation of the reaction products nor the addition of auxiliary coloring reagents.