Biogenic and Synthetic Polyamines Bind Cationic Dendrimers

Biogenic polyamines are essential for cell growth and differentiation, while polyamine analogues exert antitumor activity in multiple experimental model systems, including breast and lung cancer. Dendrimers are widely used for drug delivery in vitro and in vivo. We report the bindings of biogenic polyamines, spermine (spm), and spermidine (spmd), and their synthetic analogues, 3,7,11,15-tetrazaheptadecane.4HCl (BE-333) and 3,7,11,15,19-pentazahenicosane.5HCl (BE-3333) to dendrimers of different compositions, mPEG-PAMAM (G3), mPEG-PAMAM (G4) and PAMAM (G4). FTIR and UV-visible spectroscopic methods as well as molecular modeling were used to analyze polyamine binding mode, the binding constant and the effects of polyamine complexation on dendrimer stability and conformation. Structural analysis showed that polyamines bound dendrimers through both hydrophobic and hydrophilic contacts with overall binding constants of Kspm-mPEG-G3 = 7.6×104 M−1, Kspm-mPEG-PAMAM-G4 = 4.6×104 M−1, Kspm-PAMAM-G4 = 6.6×104 M−1, Kspmd-mPEG-G3 = 1.0×105 M−1, Kspmd-mPEG-PAMAM-G4 = 5.5×104 M−1, Kspmd-PAMAM-G4 = 9.2×104 M−1, KBE-333-mPEG-G3 = 4.2×104 M−1, KBe-333-mPEG-PAMAM-G4 = 3.2×104 M−1, KBE-333-PAMAM-G4 = 3.6×104 M−1, KBE-3333-mPEG-G3 = 2.2×104 M−1, KBe-3333-mPEG-PAMAM-G4 = 2.4×104 M−1, KBE-3333-PAMAM-G4 = 2.3×104 M−1. Biogenic polyamines showed stronger affinity toward dendrimers than those of synthetic polyamines, while weaker interaction was observed as polyamine cationic charges increased. The free binding energies calculated from docking studies were: −3.2 (spermine), −3.5 (spermidine) and −3.03 (BE-3333) kcal/mol, with the following order of binding affinity: spermidine-PAMAM-G-4>spermine-PAMMAM-G4>BE-3333-PAMAM-G4 consistent with spectroscopic data. Our results suggest that dendrimers can act as carrier vehicles for delivering antitumor polyamine analogues to target tissues

Étude de l'aspect ionique de la vision sur un modèle de membrane biologique artificielle

Si la plupart des experts s'entendent pour dire que la vue contribue pour 40 % à la connaissance tant du monde extérieur que de notre monde intérieur, ils tombent moins d'accord sur le mécanisme même du processus visuel. Certes, quelques principes ont reçu l'appui des chercheurs, mais il en reste encore qui continuent d'alimenter de vives controverses. De ceux-ci, on peut citer notamment le processus de la photo-transduction visuelle. Le but de ce travail justement est de tenter d'explorer le fondement ionique de la transduction de l'énergie lumineuse en énergie électrique, probablement le point de départ de la véritable stimulation visuelle au niveau de la membrane du photorécepteur. C'est ainsi que nous avons, pour commencer, mis au point une méthode de préparation de membranes artificielles à l'image de celle des disques des bâtonnets, méthode fondée sur la technique des couches monomoléculaires. Ces membranes artificielles, évidemment incorporées du pigment photorécepteur, la rhodopsine, ont servi à l'étude de l'effet de la lumière sur leur perméabilité aux ions. Les résultats obtenus ont permis l'établissement d'un modèle pour le mécanisme d'action des différents ions d'intérêt, à savoir le potassium, le sodium et le calcium, lors du phénomène visuel et que le Ca2+ serait un candidat valable comme transmetteur interne dans le processus de la vision

Étude de l'aspect ionique de la vision sur un modèle de membrane biologique artificielle

Si la plupart des experts s'entendent pour dire que la vue contribue pour 40 % à la connaissance tant du monde extérieur que de notre monde intérieur, ils tombent moins d'accord sur le mécanisme même du processus visuel. Certes, quelques principes ont reçu l'appui des chercheurs, mais il en reste encore qui continuent d'alimenter de vives controverses. De ceux-ci, on peut citer notamment le processus de la photo-transduction visuelle. Le but de ce travail justement est de tenter d'explorer le fondement ionique de la transduction de l'énergie lumineuse en énergie électrique, probablement le point de départ de la véritable stimulation visuelle au niveau de la membrane du photorécepteur. C'est ainsi que nous avons, pour commencer, mis au point une méthode de préparation de membranes artificielles à l'image de celle des disques des bâtonnets, méthode fondée sur la technique des couches monomoléculaires. Ces membranes artificielles, évidemment incorporées du pigment photorécepteur, la rhodopsine, ont servi à l'étude de l'effet de la lumière sur leur perméabilité aux ions. Les résultats obtenus ont permis l'établissement d'un modèle pour le mécanisme d'action des différents ions d'intérêt, à savoir le potassium, le sodium et le calcium, lors du phénomène visuel et que le Ca2+ serait un candidat valable comme transmetteur interne dans le processus de la vision

Application of photoacoustic spectroscopy in photosynthesis research

Photoacoustic spectroscopy is a new analytical technique which allows the detection of light-induced heat production due to non-radiative deactivation of light excitation. This paper gives an overview of the theory of photoacoustics and its application in photosynthesis research to measure energy conversion and storage, and for molecular structure and interaction studies as well as oxygen evolution in photosynthetic systems

Selective photoinduced Ca2+ diffusion in rhodopsin–lipid bilayers: an internal transmitter hypothesis

Triton X-100 purified rhodopsin has been incorporated into lipid bilayer membranes prepared by the combined lifting-and-touching method. The illumination of the membranes with white light and monochromatic light of λ = 498 nm resulted in a high selective increase of Ca2+ diffusion through the lipid bilayers compared to Na+ and K+. The stoichiometric ratios of photoinduced ion diffusion were found to be more than 888 Ca2+ Rh*−1 s−1 and 166 Na+ Rh*−1 s−1 at 290 K using the white light, and 1 277 Ca2+ Rh*−1 s−1, 96 K+ Rh*−1 s−1, and 50 Na+ Rh*−1 s−1 at 276 K using the monochromatic light. It was inferred that Ca2+ is an excellent candidate as internal transmitter in the visual photo-transduction

Emission of Sulfur Dioxide from Sulfite-Treated Birch Leaves

In the present paper, we report the emission of S02 from 10 mM sulfite-treated birch ( Betula papyrifera Marsh) leaves both in light and in the dark. The emission reaches maximum at around 60 min during treatment. In some leaves, maximum emission is noticed even after 5 to 10 min of initiation of sulfitetreatment. It is also observed in the presence of 3{3,4-dichlorophenyl)-1-1 dimethylurea (DCMU). However, the emission rates are higher in light than in the dark or in the presence of DCMU. This emission is not observed with sulfate-treated leaves

SO(2) Effect on Photosynthetic Activities of Intact Sugar Maple Leaves as Detected by Photoacoustic Spectroscopy

Short-term (4 hours) effect of different concentrations of SO(2) fumigation on in vivo photochemical activities of sugar maple (Acer saccharum Marsh.) leaves was investigated using photoacoustic spectroscopy. The relative quantum yield of O(2) evolution (ratio of O(2) signal to the photothermal signal) and photochemical energy storage are increased by 0.05 microliter per liter of SO(2). This increase is more pronounced in 5 to 7 year old saplings than in 3 month old seedlings. Both oxygen-relative quantum yield and energy storage of seedlings are inhibited by increased concentrations of SO(2) and the inhibition is concentration dependent. The inhibition is greater in seedlings than in saplings at 2 microliters per liter of SO(2), indicating the more susceptible nature of seedlings. The present study indicates a concentration dependent differential effect of SO(2) on photochemical activities of sugar maple leaves

Photoacoustic Analysis of Some Milk Products in Ultraviolet and Visible Light

The research reported here demonstrates the possibility of using photoacoustic spectroscopy for milk product analysis. Milk products including yogurt, cheese, and market milk were analyzed in the ultraviolet visible range. A strong absorption peak was present at 280nm for all the products. Relationship was linear between relative protein concentration of skim milk and the photoacoustic signal at 280nm (r2>.99). Powdered milks, prepared from skim milk that had been subjected to different heat treatments before drying, were analyzed, and a second absorption peak at 335nm was noted for milks subjected to high heat treatment prior to the drying process. This second absorption peak appears associated with Maillard reaction products. Analysis of stored UHT heat-treated milk and infant formulas showed a similar peak at 335nm. The results suggest that the Maillard reaction is initiated during UHT treatment of milk, and associated pigments develop only during storage. The presence of the 335-nm band in the photoacoustic spectra of infant formulas is considered as the result of heat sterilization. It is anticipated that as photoacoustic spectroscopy becomes more common, its usefulness in the milk industry, in particular, and in food science, in general, will increase

Effects of acid watering of the soil on the photosynthetic activity, growth, and foliar pigments of sugar maple saplings

Photoacoustic spectroscopy has been used to monitor the photosynthetic activity of the leaves of sugar maple saplings treated by watering the soil with simulated acid rain at different pH levels (2.S, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.6). We also measured the relative growth rate of the plants and the pigment content of leaves. The results indicated an ambivalent effect of acidity: there was a linear decline (r = 0.92) in the photosynthetic O 2 evolution as the pH of the simulated rain was lowered from 5.6 to 3.0 and a jump when it reached 25, with a stimulation effect on the relative growth rate at lower pH levels. The photochemical energy storage and the relative growth rate increased from pH 5.6 to pH 4.0-4.5, then decreased at pH 3.0 and increased again at pH 2.5. The pattern of variation of the photochemical energy storage was fairly well correlated with the pigment content of the leaves (r = 0.83). It was concluded that acid rain preferentially affects photosystem II (PSII), inhibiting O 2 evolution, and less PSI. The difference between O 2 evolution and photochemical energy storage was explained in connection with cyclic electron transport around photosystem I (PSI)