Engineering optimisation of commercial facemask formulations capable of improving skin moisturisation.

INTRODUCTION: The stratum corneum is the biggest obstacle in cosmetics with respect to skin moisturisation. Many approaches have been taken to overcome the barrier, one of which is incorporating natural cosmeceuticals into cosmetic products to enhance moisturisation effects. Here, a commercial facemask formulation was electrospun to develop dry facemasks capable of hosting cosmeceuticals within the pores of incorporated mesoporous silica. METHODS: Ethanolic solutions containing 40% w/w of the marketed facemask (7th Heaven Dead Sea peel-off facemask) and mesoporous silica were prepared and electrically processed at 30 µL min-1 at an applied voltage of 12 ± 2 kV. In vitro characterisation and release studies using fluorescein dye as a model probe were carried out. RESULTS: SEM images confirmed the fibrous nature of the resulting matrix; showing an average fiber diameter of 298.32 nm. The electrospun mask was found to be advantageous due to this fibrous nature providing high active loading capacity whilst demonstrating 100% probe release within 60 min. Contact Angle hysteresis, thermal analysis and Fourier Transform Infrared Spectroscopy (FTIR) presented evidence of compatibility and stability of and within the formulation. CONCLUSION: Adapting the formulation of a commercial polymeric facemask into an electrospun facemask has shown the versatility of the electrospinning process; now successfully crossing over into the cosmetic industry.

INTRODUCTION: La couche cornée est le premier obstacle à l'hydratation de la peau par des produits cosmétiques. De nombreuses approches ont été adoptées pour surmonter cette entrave, dont l'une consiste à intégrer des cosméceutiques naturels dans les produits cosmétiques afin d'augmenter leur pouvoir hydratant. Ici, la formulation commercialisée d'un masque pour le visage a été modifiée par électrofilage de manière à développer des masques secs pouvant intégrer des cosméceutiques dans les pores de silice mésoporeuse présent dans le produit. MÉTHODES: Des solutions éthanoliques, contenant 40 % p/p du masque pour le visage commercialisé (masque peel-off 7th Heaven Dead Sea) et de la silice mésoporeuse ont été préparées et traitées électriquement à 30 µl/min_ 1, avec une tension appliquée de 12 ± 2 kV. Des études de caractérisation et de libération in vitro ont été menées, utilisant un colorant fluorescéine en tant que sonde. RÉSULTATS: Des images SEM ont confirmé la nature fibreuse de la matrice résultante, avec un diamètre de fibre moyen s'élevant à 298,32 nm. Le masque électrofilé a été jugé avantageux en raison de sa nature fibreuse, qui permet une capacité de charge élevée, ainsi qu'une libération de 100 % de la sonde dans les 60 min. L'hystérèse de l'angle de contact, l'analyse thermique et la spectroscopie infrarouge à transformée de Fourier (IRTF) ont permis d'identifier des preuves de compatibilité et de stabilité dans cette formulation. CONCLUSION: La possibilité d'adapter la formulation d'un masque pour le visage polymérique déjà commercialisé pour en faire un masque électrofilé montre la polyvalence du processus d'électrofilage, qui fait une apparition remarquable dans le domaine des cosmétiques.

Polymeric Based Therapeutic Delivery Systems Prepared Using Electrohydrodynamic Processes.

The development of therapeutic dosage (e.g. pharmaceutical) systems is an ongoing process which, in recent times has incorporated several emerging disciplines and themes at timely intervals. While the concepts surrounding dosage forms have developed and evolved, many polymeric excipients remain as the preferred choice of materials over existing counterparts, serving functions as matrix materials, coatings and providing other specific functional properties (e.g. adhesion, controlled release and mechanical properties). There have been, however, developments in the deployment of synthetic polymeric materials (e.g. polycaprolactone, poly lactic co-glycolic acid) when compared to naturally occurring materials (e.g. lactose, gelatin). Advances in pharmaceutical process technologies have also provided novel engineering platforms to develop a host of exciting structure based materials ranging from the nanometer to the macro scales. Some of these structure enabling technologies include spray drying, super critical processing, microfluidics and even wet chemical methods. More recently electrohydrodynamic (EHDA) engineering methods have emerged as robust technologies offering potential to fabricate a plethora of generic structures (e.g. particles, fibres, bubbles and pre-determined patterns) on a broad scale range. This review focuses on key developments using various EHDA technologies for the pharmaceutical and biomaterial remits when selecting synthetic and/or naturally occurring polymers as pharmaceutical (and therapeutic) excipients. In addition, the underlying EHDA process principles are discussed along with key parameters and variables (both materials and engineering). EHDA technologies are operational at ambient conditions and recent developments have also demonstrated their viability for large scale production. These are promising technologies which have potential in established (e.g. films, dressings and microparticles) and emerging scientific themes (e.g. nanomedicines and tissue engineering).

Characterisation and mapping of gene Lr73 conferring seedling resistance to Puccinia triticina in common wheat.

KEY MESSAGE: A gene conferring seedling resistance to Puccinia triticina was mapped to chromosome 2BS in the wheat Morocco. The gene was shown to be distinct and was therefore designated Lr73. The wheat genotype Morocco, widely susceptible to isolates of Puccinia triticina, was resistant to an Australian isolate of this pathogen collected in 2004. Genetic studies established that the resistance in Morocco was also present the Australian wheat genotypes Avocet, Halberd, Harrier, Tincurrin and a selection of cultivar Warigal lacking the resistance gene Lr20. Genetic studies based on a cross with Halberd showed that the gene is dominant and located on chromosome 2BS (XwPt8760-4 cM-Lr73-1.4 cM-XwPt8235). The gene was genetically independent of the Lr13, Lr16 and Lr23 loci, also located on chromosome 2BS, indicating that it is distinct. The locus designation Lr73 was therefore assigned. On the basis of multi-pathotype tests, it is likely Lr73 is also present in the Australian wheat cultivars Clearfield STL, Federation (with Lr10), Gatcher (with Lr10 and Lr27+Lr31), Marombi (with Lr1 and Lr37), Pugsley (with Lr1 and Lr37), Spear (with Lr1), Stiletto and Tarsa (with Lr1). Gene Lr73 is unlikely to be of value in resistance breeding. However, recognising Lr73 is important to avoid its inadvertent selection in breeding programmes. Furthermore, the apparent rarity of avirulence for genes like Lr73, sometimes referred to as "fossil" resistance genes, makes them of interest in terms of the evolution of disease resistance in host plants and of virulence in the respective rust pathogens.

First Report of Resistance of Wheat Line Avocet 'S' to Stripe Rust Caused by Puccinia striiformis f. sp. tritici (Pst) in Syria.

Seedling assays and field-based assessments are common approaches used in monitoring pathogenic variability of Puccinia striiformis f. sp. tritici (Pst). Due to the many candidate genes for resistance, and the occasional presence of uncharacterized or unexpected resistance genes, interpretation of seedling and adult plant responses of stripe rust differential genotypes can be confounded. To facilitate data interpretation and overcome growth habit differences, a set of near-isogenic lines (NILs) based on a susceptible selection of the widely susceptible Australian spring wheat cultivar Avocet was developed in Plant Breeding Institute, University of Sydney. During the 2011 rust survey of major wheat growing areas in Syria, we collected and recovered two isolates, one from bread wheat and one from durum, using susceptible cultivar Morocco. Fresh urediniospores collected from inoculated seedlings of cultivar Morocco under greenhouse conditions were used to infect a differential set of seedlings comprising the Avocet S NIL series with Yr1, 5, 6, 7, 8, 9, 10, 15, 17, 27, 32, A, SP and a supplementary set of Kalyansona (Yr2), Fielder (Yr6, Yr20), Thatcher (Yr7), Federation*4/Kavkaz (Yr9), TP1295 and TP981 (Yr25), Ciano 79 and Opata 85 (Yr27), Lemhi (Yr21), Anza (YrA), Tres/6*Avocet 'S', Cook, Avocet S, and Federation following standard protocol (1). Seedling infection types (IT) were recorded 15 to 17 days post-inoculation using a 0, ;(fleck), 1 to 4 scale, with ITs 3 and 4 considered to be high. According to European race nomenclature (1), these isolates would be classified as 6 E0 and assumes that differential cultivars Lee (Yr7) and Heines Kolben should be susceptible. A low infection of ;N (necrotic areas without sporulation) was observed on Avocet S and Avocet NILs Yr1, 5, 8, 10, 15, 17, 32, A, and SP. NILs Yr6, 7, and 9 responded with high infection types. Among the supplementary set, IT ;N was recorded for Anza, Cook, Tres/6*Avocet S, Opata 85, and Ciano 79 whereas IT 3+4 occurred on Kalyansona, Fielder, Thatcher, Federation*4/Kavkaz, TP1295 and TP981, and Lemhi. Federation and Morocco were susceptible to both isolates. Based on these data we concluded that 1) Avocet S carries at least one effective gene for resistance to the two isolates (temporarily designated as YrAvS and perhaps the same as the gene(s) in Anza and Cook); and 2) since Avocet S was resistant, it was expected that all the NILs should also be resistant unless one of the selected resistance genes was closely linked in repulsion with the gene in Avocet S. Since such a situation is possible for only one line, other explanations are that the recurrent parent, Avocet S, was not genetically homogeneous, or more likely, that the genetic background of Avocet S was not fully regenerated during the six backcross and subsequent selfing generations. This work illustrates the problems that can arise when sets of differential genotypes that perform in a satisfactory way in a particular (limited) geographical area are applied globally. Pst races carrying avirulence genes that are not present in the original area where a differential cultivar is characterized for its susceptibility may be present in other areas. Consequently, a differential cultivar which was susceptible in the original area may unexpectedly exhibit resistance in a new region. Therefore, host lines considered to be "universally susceptible" in one region may not be susceptible globally. The resistance of Avocet S is yet to be characterized. Reference: (1) R. Johnson et al. Trans. Br. Mycol. Soc. 58:475, 1972.

Genetic differentiation in Pyrenophora teres f. teres populations from Syria and Tunisia as assessed by AFLP markers.

UNLABELLED: To investigate the level of genetic differentiation and diversity among Pyrenophora teres isolate populations originating from different agro-ecological areas of Syria and Tunisia and to determine the potential of AFLP profiling in genotyping Pyrenophora teres f. teres. In this study, AFLP markers have been employed to identify patterns of population structure in 20 Pyrenophora teres f. teres populations from Syria and Tunisia. Ninety-four isolates were studied by the use of a protocol that involved stringent PCR amplification of fragments derived from digestion of genomic DNA with restriction enzymes EcoRI and MesI. Based on 401 amplified polymorphic DNA markers (AFLP), variance analyses indicated that most of the variation was partitioned within rather than between populations. Genotypic diversity (GD) was high for populations from Rihane, local landraces and different agro-ecological zones (GD = 0·75-0·86). There was high genetic differentiation among pathogen populations from different host populations in Syria (Gst  = 0·31, ht = 0·190) and Tunisia (Gst  = 0·39, ht = 0·263), which may be partly explained by the low gene flow around the areas sampled. A phenetic tree revealed three groups with high bootstrap values (55, 68, 76) and reflected the grouping of isolates based on host, or agro-ecological areas. AFLP profiling is an effective method for typing the genetically diverse pathogen Pyrenophora teres f. teres. SIGNIFICANCE AND IMPACT OF THE STUDY: The study represents a comparative analysis of the genetic diversity in P. teres isolates from two countries spanning two continents and also shows that several distinct P. teres genotypes may be found in a given environment. The implications of these findings for Pyrenophora teres f. teres evolutionary potential and net blotch-resistance breeding in Syria and Tunisia were also discussed.

Comparative virulence of Pyrenophora teres f. teres from Syria and Tunisia and screening for resistance sources in barley: implications for breeding.

AIMS: The aim of this study is to investigate the pathogenic diversity and virulence groups among Pyrenophora teres f. teres isolates, sampled from Syria and Tunisia, and to identify the most effective source of resistance in barley that could be used in breeding programmes to control net blotch in both countries. METHODS AND RESULTS: One hundred and four isolates of P. teres f. teres were collected from barley in different agroecological zones of Tunisia and Syria. Their virulence was evaluated using 14 barley genotypes as differential hosts. The UPGMA clustering identified high pathogenic variability; the isolates were clustered onto 20 pathotypes that were sheltered under three virulence groups, with high, intermediate and low disease scores. According to susceptibility/resistance frequencies and mean disease ratings, CI05401 cultivar ranked as the best differential when inoculated with the Syrian isolates. However, CI09214 cultivar was classified as the best effective source of resistance in Tunisia. CONCLUSIONS: All P. teres f. teres isolates were differentially pathogenic. CI09214 and CI05401 cultivars were released as the most effective sources of resistance in Syria and Tunisia. SIGNIFICANCE AND IMPACT OF THE STUDY: National and international barley breeding programmes that seek to develop resistance against P. teres f. teres in barley should strongly benefit from this study. This resistance cannot be achieved without the proper knowledge of the pathogen virulence spectrum and the sources of host resistance.

Biocatalytic synthesis of polymeric nanowires by micellar templates of ionic surfactants.

Micelle-templated polyguaiacol nanowires were successfully prepared via polymerization oxidation of guaiacol (o-methoxy phenol) by peroxidase enzyme in the presence of hydrogen peroxide at mild reaction conditions. The dimensions of the prepared nanowires were controlled by tuning the size and shape of the micelle structure via changing and controlling the type, chain length and molar concentrations of the ionic surfactant. The progress of the reaction and estimation of the size of soft micellar templates were followed by UV-Vis spectroscopy and dynamic light scattering (DLS). The resulting micelle encapsulated or purified polyguaiacol nanowires were characterized using transmission electron microscopy (TEM).

Detection of Wheat Stem Rust (Puccinia graminis f. sp. tritici) Race TTKSK (Ug99) in Iran.

In 2007, new reports of stem rust caused by Puccinia graminis Pers. f. sp. tritici Eriks. in Lorestan and Hamadan provinces of Iran were considered unusual because stem rust had not been recorded previously in the Hamadan area where winter habit wheat cultivars are grown. Detailed investigations in these areas showed significant levels of stem rust in experimental plots and occasionally in farmers' fields, some that showed moderate to high levels of infection. Race analysis of four stem rust samples collected from Borujerd, Hamadan, and Poldokhtar (southwest) and Kelardasht (north) in 2007 was conducted using a modified North American Pgt differential set representing the resistance genes Sr5, 6, 7b, 8a, 9a, 9b, 9d, 9e, 9g, 10, 11, 17, 21, 24, 30, 31, 36, 38, Tmp, and McN, commercial cultivars, and genotypes known to carry the 1B.1R translocation. A race collected from Borujerd in 1997 was also included for comparison. Tests were carried out under standard controlled conditions (1,2). Two isolates from samples collected from Borujerd and Hamadan in 2007 showed high infection types (ITs 33+ to 4) on differential lines carrying resistance genes Sr5, 6, 7b, 8a, 9a, 9b, 9d, 9e, 9g, 10, 11, 17, 21, 30, 31, 38, and McN, and low ITs of ;C1= to 2=, ;C to ;N1=, and 2+ on lines carrying Sr24, Sr36, and SrTmp, respectively. On the basis of the high/low ITs on the 20 differentials in the modified Pgt differential set of North America, the two isolates of Pgt collected from Borujerd and Hamadan in 2007 were identified as race TTKSK. The two isolates from samples collected from Poldokhtar and Kelardasht in 2007 and the isolate collected from Borujerd in 1997 were identified as races TRFSC, TTJQC, and RRHSC, respectively. Race TTKSK identified in the current study produced high ITs of 3+ to 4 on the wheat genotypes Line E*4/Kavkaz, Fed.*4/Kavkaz, Clement, and Mildress and commercial cultivars Falat (Seri 82), Shiroodi (CIMMYT name Attila and Indian name PBW343), Atrak (Kauz), and MV17, all carrying the 1BL.1RS translocation and further confirming virulence for Sr31. The spread of Ug99 to Kenya (1999 to 2002), Ethiopia (2003), and Yemen (2006) suggests progressive migration from Uganda, following the pattern believed to have occurred for the spread of wheat stripe rust pathogen from East Africa in 1986 to India in 1998 (3). Our results are consistent with the TTKSK race identified in Iran migrating from the new African population. Seedling evaluation of Iranian wheat cultivars and advanced lines to isolates of TTKSK from Iran confirmed full susceptibility. These results reinforce the serious threat of race TTKSK to wheat production in Iran. In conclusion, the occurrence of race TTKSK in Iran, the susceptibility of Iranian wheat cultivars to this race, the presence of environmental conditions conducive to disease epidemics in different parts of the country, and the occurrence of the alternate host barberry in many of the mountainous areas of Iran, indicate a new and serious threat to wheat production in Iran and a potentially serious threat to neighboring countries. References: (1) Y. Jin et al. Plant Dis. 91:1096, 2007. (2) Z. A. Pretorius et al. Plant Dis. 84:203, 2000. (3) R. P. Singh et al. CAB Rev. 1 (No. 054), 2006.

Spectrophotometric assay for horseradish peroxidase activity based on pyrocatechol-aniline coupling hydrogen donor.

The hydrogen donor couples pyrocatechol-aniline and phenol-aminoantipyrine in the presence of hydrogen peroxide were compared as chromogens for horseradish peroxidase (HRP) assay. UV-Visible spectroscopy and high-performance liquid chromatography analysis indicated that during the HRP biocatalytic process, pyrocatechol-aniline was converted to a pink-colored reagent with a lambda(max) of 510 nm, which was used in the assay of HRP activity. Electrochemical studies revealed adequate electron transfer ability for this color reagent to serve as a proper mediator for HRP also. Using pyrocatechol-aniline a higher sensitivity and lower detection limit was obtained relative to those of the phenol-aminoantipyrine couple, which is commonly used for HRP assay. A relative standard deviation of 2.9% was obtained for 20 HRP activity measurements, indicating a satisfactory reproducibility for this method. In addition, kinetic parameters of K(m) (12.5mM) and V(max) (12.2 mM min(-1)mg(-1)) were calculated for pyrocatechol-aniline. Regarding the superiority of pyrocatechol-aniline, this couple is suggested to be a better hydrogen donor for the HRP spectrophotometric assay.

Suicide-peroxide inactivation of microperoxidase-11: a kinetic study.

The kinetics of microperoxidase-11 (MP-11) in the oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H2O2. Concentrations of substrates were so selected that: 1) the reaction was first-order in relation to benign substrate, AH and 2) high ratio of suicide substrate to the benign substrate, [H2O2] >> [AH]. Validation and reliability of the obtained kinetic equations were evaluated in various nonlinear and linear forms. Fitting of experimental data into the obtained integrated equation showed a close match between the kinetic model and the experimental results. Indeed, a similar mechanism to horseradish peroxidase was found for the suicide-peroxide inactivation of MP-11. Kinetic parameters of inactivation including the intact activity of MP-11, alphai, and the apparent inactivation rate constant, ki, were obtained as 0.282 +/- 0.006 min(-1) and 0.497 +/- 0.013(-1) min at [H2O2] = 1.0 mM, 27 degrees C, phosphate buffer 5.0 mM, pH = 7.0. Results showed that inactivation of microperoxidase as a peroxidase model enzyme can occur even at low concentrations of hydrogen peroxide (0.4 mM).

The effects of three diets on some growth performance of whitefish (Coregonus lavaretus) fry.

In a 3 months experiment, the effects of three different kinds of food rations including culture rotifers, commercial food and the equal amount mixture of these two foods were studied on some growth specifications and survival of the whitefish (Coregonus lavaretus) fry. The initial average weight and length of the fry were 0.009 g and 4 mm, respectively. The period of experiment was among April to July 2003. The assessed characteristics variance analysis showed that the different food treatments caused very significant differences among the all averages (p < 0.01). Comparing the characteristics averages showed that during the first month of experiment, the best results of weight (0.029 g), total length (8.78 mm), specific growth rate (5.36%) and food efficiency (63.48%) were obtained in live food treatment, whereas the weakest averages of referred characteristics were observed in commercial food treatment. During the last month of experiment, some of the above results reversed so that the best averages of specific growth rate (3.73%) and food efficiency (44.3%) were observed in commercial food treatment. The results of this study showed that the use of rotifer as live food for fry has provided better survival rate than the other two treatments. However, this food could not provide the best results for the all measured characteristics in all of the experiment period, for the reason that during the third month of experiment period, using commercial food treatment which consist of more miscellaneous nutrient components, created better results for some fry's characteristics than the live food.

Denaturation of jack-bean urease by sodium n-dodecyl sulphate: a kinetic study below the critical micelle concentration.

Kinetics of urease denaturation by anionic surfactant (sodium n-dodecyl sulphate, SDS) at concentrations below the critical micelle concentration (CMC) is investigated spectrophotometrically at neutral pH and the corresponding two-phase kinetic parameters of the process are estimated from a three-state reversible process using a binomial exponential relation based on the relaxation time method as: Using a prepared computer program, the experimental data are properly fitted into a binomial exponential relation, considering a two-phase denaturation pathway including a kinetically stable folded intermediate formed at SDS concentration of 1.1 mM. Forward and backward rate constants are estimated as: k(1)=0.2141+/-4.5 x 10(-3), k(2)=5.173 x 10(-3)+/-8.3 x 10(-5), k(-1)=0.09432+/-3.6 x 10(-4) and k(-2)=2.079 x 10(-3)+/-5.6 x 10(-5)s(-1) for the proposed mechanism. The rate-limiting step as well as the reaction coordinates in the denaturation mechanism are established. The mechanism involves formation of a kinetically stable folded native like intermediate through the electrostatic interactions. The intermediate was found to be more stable even than the native form (by about 9 kJmol(-1)) and still hexamer, because no loss of amplitude was observed. Electrophoresis experiments on the native and surfactant/urease complexes indicated a higher mobility for the kinetically folded native like intermediate.

Suicide-peroxide inactivation of horseradish peroxidase in the presence of sodium n-dodecyl sulphate: a study of the enzyme deactivation kinetics.

In the presence of the anionic surfactant sodium n-dodecyl sulphate (SDS), horseradish peroxidase (HRP) undergoes a deactivation process. Suicide inactivation of horseradish peroxidase by hydrogen peroxide(3 mM) was monitored by the absorbance change in product formation in the catalytic reaction cycle. The progress curve of the catalytic reaction cycle was obtained at 27degrees C and phosphate buffer 2.5 mM (pH = 7.0). The corresponding kinetic parameters i.e., intact enzyme activity (alpha i); the apparent rate constant of suicide inactivation by peroxide (ki); and the apparent rate constants of enzyme deactivation by surfactant (kd) were evaluated from the obtained kinetic equations. The experimental data are accounted for by the equations used in this investigation. Addition of SDS to the reaction mixture intensified the inactivation process. The deactivation ability of denaturant could be resolved from the observed inactivation effect of the suicide substrate by applying the proposed model. The results indicate that the deactivation and the inactivation processes are independent of each other.

A distinct intermediate of RNase A is induced by sodium dodecyl sulfate at its pK(a).

The chemical denaturation of RNase A was found to be mediated by sodium dodecyl sulfate (SDS) at various pH. The characterization of the unfolding pathway was investigated by spectrophotometry and differential scanning calorimetry (DSC), and was analyzed by multivariate curve resolution (MCR) as a chemometric method. The spectrophotometric titration curve of RNase A upon interaction with SDS indicated a distinct complex intermediate in glycine buffer at pH 3.3. This was accompanied with the catalytic activation of the enzyme and was concurrent with maximum population of the intermediate, determined by MCR. This was confirmed by the DSC profile of RNase A in the presence of SDS, indicated by two transitions in thermal unfolding. The kinetic data on the unfolding process of RNase A upon addition of SDS showed a two-phase pathway under the same conditions. The intermediate appeared at low pH especially at the pK(a) of SDS (pH 3.3). These results provide strong evidence of the influence of low pH (around the pK(a) of SDS) on the existence of an intermediate upon interaction of RNase A with SDS.

Effect of Mn2+, Co2+, Ni2+, and Cu2+ on horseradish peroxidase: activation, inhibition, and denaturation studies.

The effects of transition metal ions (M2+) such as Mn2+, Co2+, Ni2+, and Cu2+ on the functional and structural stabilities of horseradish peroxidase (HRP) were investigated with respect to reversible chemical denaturation, Michaelis-Menten kinetics, chemical modification and time-dependent catalytic activity. Conformational Gibbs free energy (deltaGo(H2O)) as a structural stability criterion and transition concentrations of metal ions ([M2+] 1/2) were estimated using a two-state chemical denaturation model. Activation and inhibitory concentration ranges for each metal ion were specified by the steady-state enzyme kinetics. Results of a pH-profile method confirmed by chemical modification indicate that a histidine residue interacts in the activation concentration range, whereas carboxylic residues (Asp and Glu) contribute to interaction in the inhibitory concentration range. Incubation of the enzyme with the metal ion at activation concentration leads to long-term functional stability of peroxidase. Thus, such metal ions as potent effectors induced the enhancement of conformational and functional stabilities of horseradish peroxidase.

A new method for separation of 131I, produced by irradiation of natural uranium.

Separation of 131I from natural uranium fission product mixtures has been accomplished by sorbing the 131I on special platinum-charcoal sorbent and desorbing by buffer solution (NaHCO3+Na2S2O3). High radiochemical and chemical purity is obtained by this method. Important parameters such as temperature, distillation rate, sorbing and desorbing rates and 131I separation yields have been investigated.

Transpupillary thermotherapy (TTT) for age-related macular degeneration.

PURPOSE: To review the results of transpupillary thermotherapy (TTT) on choroidal neovascular membranes associated with age-related macular degeneration (AMD). MATERIALS AND METHODS: 35 eyes of 35 patients with AMD and choroidal neovascularization and exudation were treated with TTT and had fundus photographs and fluorescein angiography (FA) before and at least six months after TTT. 28 eyes had predominantly occult lesions as seen on FA, while 7 demonstrated primarily classic lesions. All were treated with 650mw power or less using the 810 nm diode laser (3000 micron spot, duration of 60 seconds). Visual acuity, lesion size, and amount of subretinal fluid were determined by results of examination and review of photographs and fluorescein angiograms. RESULTS: A 50% reduction in subretinal fluid was achieved in 67% of treated eyes overall, with stabilization of vision (less than three lines of visual acuity lost) in 86%. Complications from treatment were infrequent (9%) and involved hemorrhage noted in the region of treatment upon follow-up. CONCLUSION: TTT promotes resolution of subretinal fluid and appears to stabilize visual acuity in patients with exudative AMD.

Suicide inactivation of peroxidase by H2O2: kinetic equations for peroxidatic oxidation reaction of guaiacol and determination of the kinetic parameters.

The kinetics of horseradish peroxidase (HRP) in oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H2O2. Those ranges of concentrations were selected in which: 1) the reaction was first-order in relation to [AH] and 2) [H2O2] >> [AH]. By combination of rate equations of the two concurrent reactions, consumption of AH and suicide inactivation of HRP, the overall kinetic equations were obtained which define the progress curve of reactions. The compatibility between equations and kinetic behaviour of reaction were evaluated in different ways. A close match was found between equations and experimental data. These equations can be used for determining 1) intact value of enzyme activity at start time of reaction and 2) apparent rate constant of suicide inactivation (ki') in a given concentration of H2O2, by processing of the data of the progress curve. The ki' value was found to be 0.178 +/- 0.003 min.-1 at 10 mM of H2O2 and 0.04 +/- 0.002 at 3 mM H2O2, at 27 degrees C and sodium phosphate buffer, pH = 7.0.

Denaturation of horseradish peroxidase with urea and guanidine hydrochloride.

Favourable effects of urea and guanidine hydrochloride (Gdn HCl) on solubilization of the polar, non-polar and peptide groups of horseradish peroxidase (HRP), an example of a globular protein, provide the driving force for unfolding of HRP, in a reversible two-state process. The intrinsic or conformational stability of HRP at various pH values and temperatures has been estimated by the linear extrapolation method (LEM), a denaturant binding model (DBM) and Tanford's model. There is good agreement between these methods. Tanford's model shows that urea interacts with non-polar groups to a greater extent than Gdn HCl does, whereas Gdn HCl interacts more effectively with the peptide groups of HRP.