Impact of UHT treatment and storage on liquid infant formula: Complex structural changes uncovered by centrifugal field-flow fractionation with multi-angle light scattering

Protein modifications in liquid infant formula (IF) have been widely studied, but distinguishing between heat- and storage-induced structural changes remains challenging. A generic liquid IF was subjected to direct or indirect UHT treatment and stored at 40 °C up to 180 days. Colour and pH were monitored and structural changes were characterised by dynamic light scattering, SDS-PAGE and centrifugal field-flow fractionation (FFF) coupled with multi-angle light scattering (MALS) and UV detectors to evaluate whether heat-induced differences would level out during storage. Both direct- and indirect UHT treatment led to structural changes, where the higher heat load of the indirect UHT treatment caused more pronounced changes. Indications were that storage-induced changes in pH, browning and non-reducible cross-links were not dependent on UHT treatment. However, FFF-MALS-UV analysis allowed characterisation of complex aggregates, where structural changes continued to be most pronounced in indirect UHT treated samples, and different storage-induced aggregation behaviour was observed.

High stability and cooperative unfolding of α-synuclein oligomers

Many neurodegenerative diseases are linked with formation of amyloid aggregates. It is increasingly accepted that not the fibrils but rather oligomeric species are responsible for degeneration of neuronal cells. Strong evidence suggests that in Parkinson's disease (PD), cytotoxic α-synuclein (αSN) oligomers are key to pathogenicity. Nevertheless, insight into the oligomers' molecular properties remains scarce. Here we show that αSN oligomers, despite a large amount of disordered structure, are remarkably stable against extreme pH, temperature, and even molar amounts of chemical denaturants, though they undergo cooperative unfolding at higher denaturant concentrations. Mutants found in familial PD lead to slightly larger oligomers whose stabilities are very similar to that of wild-type αSN. Isolated oligomers do not revert to monomers but predominantly form larger aggregates consisting of stacked oligomers, suggesting that they are off-pathway relative to the process of fibril formation. We also demonstrate that 4-(dicyanovinyl)julolidine (DCVJ) can be used as a specific probe for detection of αSN oligomers. The high stability of the αSN oligomer indicates that therapeutic strategies should aim to prevent the formation of or passivate rather than dissociate this cytotoxic species.

The role of stable α-synuclein oligomers in the molecular events underlying amyloid formation

Studies of proteins' formation of amyloid fibrils have revealed that potentially cytotoxic oligomers frequently accumulate during fibril formation. An important question in the context of mechanistic studies of this process is whether or not oligomers are intermediates in the process of amyloid fibril formation, either as precursors of fibrils or as species involved in the fibril elongation process or instead if they are associated with an aggregation process that is distinct from that generating mature fibrils. Here we describe and characterize in detail two well-defined oligomeric species formed by the protein α-synuclein (αSN), whose aggregation is strongly implicated in the development of Parkinson's disease (PD). The two types of oligomers are both formed under conditions where amyloid fibril formation is observed but differ in molecular weight by an order of magnitude. Both possess a degree of β-sheet structure that is intermediate between that of the disordered monomer and the fully structured amyloid fibrils, and both have the capacity to permeabilize vesicles in vitro. The smaller oligomers, estimated to contain ∼30 monomers, are more numerous under the conditions used here than the larger ones, and small-angle X-ray scattering data suggest that they are ellipsoidal with a high degree of flexibility at the interface with solvent. This oligomer population is unable to elongate fibrils and indeed results in an inhibition of the kinetics of amyloid formation in a concentration-dependent manner.

Wildtype and A30P mutant alpha-synuclein form different fibril structures

Parkinson's Disease (PD) is a neurodegenerative movement disorder affecting millions of people worldwide. One of the key players in the development of the disease is the protein α-synuclein (aSN), which aggregates in the brain of PD patients. The aSN mutant A30P has been reported to cause early-onset familial PD and shows different aggregation behavior compared to wt aSN. Here we use a multidisciplinary approach to compare the aggregation process of wt and A30P aSN. In agreement with previous studies, we observe an initial lag phase followed by a continuous structural development of fibrils until reaching an apparent monomer-aggregate equilibrium state and a plateau in Thioflavin T (ThT) fluorescence intensity. However, at later timepoints A30P shows greater propensity than αSN wt to form dense bundled fibril networks. Combining small angle x-ray scattering, x-ray fibre diffraction and linear dichroism, we demonstrate that while the microscopic structure of the individual fibril essentially remains constant throughout the experiment, the formation of dense A30P fibril networks occur through a continuous assembly pathway while the formation of less dense wt fibril networks with fewer contact points follows a continuous path during the elongation phase and a second rearrangement phase after reaching the ThT fluorescence plateau. Our work thus highlights that structural rearrangements proceed beyond the plateau in ThT-based monitoring of the fibrillation process, and the density and morphology of the resulting fibril networks is highly dependent on the aSN form studied.

Formation of dynamic soluble surfactant-induced amyloid β peptide aggregation intermediates

Intermediate amyloidogenic states along the amyloid β peptide (Aβ) aggregation pathway have been shown to be linked to neurotoxicity. To shed more light on the different structures that may arise during Aβ aggregation, we here investigate surfactant-induced Aβ aggregation. This process leads to co-aggregates featuring a β-structure motif that is characteristic for mature amyloid-like structures. Surfactants induce secondary structure in Aβ in a concentration-dependent manner, from predominantly random coil at low surfactant concentration, via β-structure to the fully formed α-helical state at high surfactant concentration. The β-rich state is the most aggregation-prone as monitored by thioflavin T fluorescence. Small angle x-ray scattering reveals initial globular structures of surfactant-Aβ co-aggregated oligomers and formation of elongated fibrils during a slow aggregation process. Alongside this slow (minutes to hours time scale) fibrillation process, much faster dynamic exchange (k(ex) ∼1100 s(-1)) takes place between free and co-aggregate-bound peptide. The two hydrophobic segments of the peptide are directly involved in the chemical exchange and interact with the hydrophobic part of the co-aggregates. Our findings suggest a model for surfactant-induced aggregation where free peptide and surfactant initially co-aggregate to dynamic globular oligomers and eventually form elongated fibrils. When interacting with β-structure promoting substances, such as surfactants, Aβ is kinetically driven toward an aggregation-prone state.

Proteolytic activation of proteose peptone component 3 by release of a C-terminal peptide with antibacterial properties

The milk protein proteose peptone component 3 (PP3, also known as lactophorin) is a small phosphoglycoprotein, which is exclusively expressed in the lactating mammary gland. A 23-residue synthetic peptide (lactophoricin, Lpcin S), corresponding to the C-terminal amphipathic α-helix of PP3, has previously been shown to permeabilize membranes and display antibacterial activity. Lactophorin readily undergoes proteolytic cleavage in milk and during dairy processing, and it has been suggested that PP3-derived peptides are part of milk's endogenous defense system against bacteria. Here, we report that a 26-residue C-terminal peptide (Lpcin P) can be generated by trypsin proteolysis of PP3 and that structural and functional studies of Lpcin P indicate that the peptide has antibacterial properties. The Lpcin P showed α-helical structure in both anionic and organic solvents, and the amount of α-helical structure was increased in the presence of lipid vesicles. Oriented circular dichroism showed that Lpcin P oriented parallel to the membrane surface. However, the peptide permeabilized calcein-containing vesicles efficiently. Lpcin P displayed antibacterial activity against Streptococcus thermophilus, but not against Staphylococcus aureus and Escherichia coli. The PP3 full-length protein did not display the same properties, which could indicate that PP3 functions as a precursor protein that upon proteolysis, releases a bioactive antibacterial peptide.

Small-scale mantle convection produces stratigraphic sequences in sedimentary basins

Cyclic sedimentary deposits link stratigraphic sequences that are now geographically distant but were once part of the same depositional environment. Some of these sequences occur at periods of 2 to 20 million years, and eustatic sea-level variations or regional tectonic events are likely causes of their formation. Using numerical modeling, we demonstrate that small-scale mantle convection can also cause the development of stratigraphic sequences through recurrent local and regional vertical surface movements. Small-scale convection-driven stratigraphic sequences occur at periods of 2 to 20 million years and correlate only at distances up to a few hundred kilometers. These results suggest that previous sequence stratigraphic analyses may contain erroneous conclusions regarding eustatic sea-level variations.

Energy intake variability in free-living young children

It has been suggested that young children regulate their daily energy intake very closely with highly stable day-to-day total energy intake. This hypothesis was developed on the basis of an experimental study of 15 children aged 26 to 62 months, which reported a within-subject coefficient of variation (CV) in daily energy intake of 10.4%. We tested the hypothesis that free-living energy intakes were highly stable on a day-to-day basis in a sample of free-living young children from Glasgow, Scotland. In 101 children (47 boys) aged 2.6-6.8 years, energy intake was measured using multiple-pass 24-h recalls. Within-subject CV was 19.2%, which was significantly higher than the 10.4% reported by previously Birch and colleagues (p<0.0001). In addition, we identified four other studies on free-living children with within-subject CVs ranging from 16.1-28.7%. This evidence indicates that young children show a wide intra-individual variation in day-to-day regulation of energy intake in a free-living environment.

Vibrationally resolved photoabsorption spectroscopy of red fluorescent protein chromophore anions

Photoabsorption studies of red fluorescent protein chromophore anions have been performed at the ELISA electrostatic heavy-ion storage ring. The broad absorption band due to electronic excitation of the chromophores is tuned to a longer wavelength (redshifted) by extending the electronic conjugation of the molecule. A clear vibrational progression is resolved with E(vib) approximately 380 and 520 cm(-1) for two different forms of the chromophore. The vibrational modes correspond to collective motions of the entire molecular structure. It is argued that the excited electronic state has an equilibrium configuration far from that of the electronic ground state, i.e., poor Franck Condon overlap.

Does serum cholesterol contribute to vertebral bone loss in postmenopausal women?

Recent in vitro and animal studies suggest that cholesterol and its metabolites inhibit the functional activity of osteoblasts and thereby induce reduced bone mineralization. However, scant information is available on the clinical implication of these findings with special regard to postmenopausal bone loss. Therefore, the aim of the present study was to investigate cross-sectional and longitudinal associations between serum cholesterol, bone mineral density (BMD), and bone turnover in 340 postmenopausal women aged 50-75 years (mean 59 years), who were followed for 8.3 +/- 1.1 years. BMD in the lumbar spine, distal forearm, and total hip was measured by dual energy X-ray absorptiometry. Other study variables were physical measures, serum cholesterol, serum markers of bone turnover, and self-reported information on various risk factors for osteoporosis. At baseline, serum cholesterol showed significant negative correlation with BMD at the lumbar spine (r = -0.21, P < 0.0001) and distal forearm (r = -0.14, P = 0.013), but not at the hip. No associations of serum cholesterol with serum osteocalcin (r = 0.054, P = 0.317) and CTX (r = -0.027, P = 0.623) were, however, noted. After adjustment for age and BMI, the negative correlation remained significant at the lumbar spine (r = -0.16, P = 0.004), but not at the distal forearm (r = -0.018, P = 0.738). At the end of the 8-year follow-up, the correlation between serum cholesterol and spine BMD was not observed. Those with the largest increases in serum cholesterol, however, showed the greatest decreases in spine BMD independently of the changes in BMI (r = -0.16, P = 0.004). The correlation between the changes in serum cholesterol and the simultaneous changes in osteocalcin (r = 0.081, P = 0.140) and CTX (r = 0.042, P = 0.441) were statistically insignificant. Thus, our results suggest that the weak associations between spine BMD and serum cholesterol can be explained by the fact that both variables are simultaneously affected by estrogen deficiency rather than by a direct influence of serum cholesterol on osteoblast function.

Aging, intergenerational distribution and public pension systems

"This paper develops an intertemporal simulation model capable of addressing the macroeconomic and distributional effects of demographic shocks in a small open economy. Two sources of population aging are examined, viz. lower birth rates and prolonged expected lifetimes at retirement age. Due to strong expectational effects, both shocks are found to change average consumption in a downward direction, in the short run as well as in the long run. This effect is matched by a strong net acquisition of foreign assets. Furthermore, it turns out that the intergenerational distribution of the burden of adjusting to an aging population is strongly dependent on whether the benefit rate, the contribution rate, or the relative non-capital income of pensioners and workers is held fixed."

Absorption spectrum of the green fluorescent protein chromophore anion in vacuo

A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein. Its absorption characteristics are therefore ascribed to intrinsic chemical properties of the chromophore. Evidently, the special beta-can structure of the protein provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains.

On the formation of radical dications of protonated amino acids in a "microsolution" of water or acetonitrile and their reactivity towards the solvent

In high-energy collisions (50 keV) between O2 and protonated amino acids AH+, radical dications AH2+* are formed for A = Phe, His, Met, Tyr, and Trp. When solvated by water or acetonitrile (S), AH2+*(S)1,2 are formed for A = Arg, His, Met, Tyr, and Trp. The stability of the hydrogen-deficient AH2+* in the "microsolution" depends on the energetics of the electron transfer reaction AH2+* +S --> AH++S+*, the hydrogen abstraction reaction AH2+*+S --> AH2(2+)+[S-H]*, and the proton transfer reaction AH2+* + S --> A+*+SH+. Using B3LYP/ 6-311+G(2d,p)//B3LYP/6-31+G(d) model chemistry, we describe these three reactions in detail for A=Tyr and find that the first two reactions are unfavorable whereas the third one is favorable. However, energy is required for the formation of Tyr+* and SH+ from TyrH2+*(S) to overcome the Coulomb barrier, which renders the complex observable with a life-time larger than 5 micros. The ionization energy, IE, of TyrH+ is calculated to be 11.1 eV in agreement with an experimental measurement of 10.1+/-2.1 eV ([IE(CH3CN)+IE(Tyr)]/ 2); hydration further lowers the IE by 0.3 eV [IE(TyrH+(H2O) = 10.8 eV, calculated]. We estimate the ionization energies of TrpH+, HisH+, and MetH+ to be 10.1+/-2.1 eV, 12.4+/-0.2 eV, and 12.4+/-0.2 eV, and that of PheH+ to be larger than 12.6 eV.

Electron loss from multiply protonated lysozyme ions in high energy collisions with molecular oxygen

We report on the electron loss from multiply protonated lysozyme ions Lys-Hn(n)+ (n = 7 - 17) and the concomitant formation of Lys-Hn(n+1)+. in high-energy collisions with molecular oxygen (laboratory kinetic energy = 50 x n keV). The cross section for electron loss increases with the charge state of the precursor from n = 7 to n = 11 and then remains constant when n increases further. The absolute size of the cross section ranges from 100 to 200 A2. The electron loss is modeled as an electron transfer process between lysozyme cations and molecular oxygen.

Anthelmintic screening of Zimbabwean plants traditionally used against schistosomiasis

Extracts of 23 plant species used popularly against schistosomiasis in Zimbabwe were screened for their anthelmintic effect. Schistosomules of the trematode Schistosoma mansoni and cysticercoids of the cestode Hymenolepis diminuta were studied in vitro. The material consisted of 58 plant extracts, of which 37 killed the newly excysted cysticercoids within an hour, when incubated in a culture medium. Lethal concentrations varied from 0.8 to 103 mg/ml. All plant extracts showed activity against the tapeworms after 24 h. Ten of the best extracts were also tested against schistosomules. Five of these extracts showed activity. Lethal concentrations varied from 0.6 to 33.8 mg/ml of dry plant material. Extracts of stem and root from Abrus precatorius (Fabaceae), of root bark and leaves from Ozoroa insignis (Anacardiaceae) and of root bark from Zizyphus mucronata (Rhamnaceae) gave the best results against tapeworms. The best results against schistosomules were obtained with stem and root extracts from Abrus precatorius (Fabaceae) and stem bark from Elephantorrhiza goetzei (Mimosaceae). Although the activity of root and root bark extracts commonly used in traditional medicine was verified in this study, our results showed that also extracts from leaf and stem can be effective anthelmintics.

Isolating the spectroscopic signature of a hydration shell with the use of clusters: superoxide tetrahydrate

Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O(2)-. (H(2)O)(n) (n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the pi* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.

Earthquakes on dipping faults: the effects of broken symmetry

Dynamic simulations of earthquakes on dipping faults show asymmetric near-source ground motion caused by the asymmetric geometry of such faults. The ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more, given identical initial stress magnitudes. The motion of the hanging wall is larger than that of the footwall in both thrust (reverse) and normal earthquakes. The asymmetry between normal and thrust (reverse) faults results from time-dependent normal stress caused by the interaction of the earthquake-generated stress field with Earth's free surface. The asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault.