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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 1 (1982), S. 637-647 
    ISSN: 0392-6737
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono state determinate le grandezze ΔG 0, ΔH 0, ΔS 0 and ΔC p 0 relative alla chinacrina, un derivato acridinico, legata ai seguenti DNA nativi: timo di vitello, Escherichia Coli e Micrococcus Luteus. Al fine di determinare la «costante» di associazione all'equilibrio per complessi tra 20 e 70°C si è fatto uso della spettrofotometria del singolettoS 1 della chinacrina. I valori di ΔG 0 sono stati trovati quasi costanti attorno a −7 kcal/mol, mentre ΔH 0 mostra una grande variazione nei suoi valori, da ∼−3 a ∼−7 kcal/mol. I dati mostrano anche che l'associazione alle piú basse temperature è governata sia da entalpia che entropia, mentre alle piú alte temperature il contributo entalpico domina il meccanismo d'intercalazione.
    Abstract: Реэюме Вычисляются термодинамические величины ΔG 0, ΔH 0, ΔS 0 и ΔC p 0 для хинакрина, проиэводной акридина, свяэанного в раэличных природных DNA. Испольэуется спектроскопия оптического поглощения в областиS 1 синглета хинакрина для определения «постоянных» равновесной ассоции комплексов в интервале температур между 20 и 70°C. Получена почти постоянная величина ΔG 0, блиэкая к ∼−7 ккая/моль, тогда как величина ΔH 0 обнаруживает большое иэменение с темиературой от ∼−3 до ∼−7 ккал/моль. Полученные данные покаэывают, что при более ниэких температурах ассоциация определяется и энтальпией и энтропией, тогда как при более высоких температурах энтальпия определяет доминирующий вклад в механиэм внедрения.
    Notes: Summary The thermodynamical quantities ΔG 0, ΔH 0, ΔS 0 and ΔC p 0 have been evaluated for quinacrine, an acridine derivative, bound to different native DNAs: calf thymus, E. Coli and M. Luteus. Optical-absorption spectroscopy at theS 1 singlet of quinacrine has been employed in order to determine the equilibrium association «constant» of the complexes between 20 and 70°C. A nearly constant value of ΔG 0 has been evaluated, close to −7 kcal/mol, whereas ΔH 0 has been found to display a large change with temperature, from ∼−3 to ∼−7 kcal/mol. The data show also that at lower temperatures the association is both enthalpy and entropy controlled, whereas at higher temperatures the enthalpy becomes the dominant contribution to the intercalation process.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 11 (1989), S. 745-759 
    ISSN: 0392-6737
    Keywords: Interactions with radiations at the molecular level ; luminescence ; Scattering, diffraction, dispersion and polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto È stato messo a punto un apparato per misure di light scattering dinamico (DLS), tecnica di grande utilità per lo studio della conformazione e della dinamica delle macromolecole. In questo lavoro si è studiato un DNA circolare, PACL29, di 5400 paia di basi, peso molecolare 3.27·106 daltons, e si sono separate due componenti esponenziali nella funzione di correlazione ricavando pertanto due coefficienti di diffusione. Il primo corrisponde al moto traslazionale (D=(2.9±0.3)·108cm2/s), mentre ai moti interni corrisponde un coefficiente di diffusioneD i=(11.7±0.3)·108cm2/s con un tempo di rilassamento interno τi=(850±200)μs.
    Abstract: Резюме Собрана и испытана аппаратура для динамического рассеяния света на растворах. Предложенная техника динамического рассеяния света удобна для исследования конформации и динамики макромолекул. В этой работе исследуется кольцевая ДНК, PACL 29, (молекулярный вес ≃ 3,27 106 Дальтон) и выделяются две компоненты коэффициента диффузии. Первая компонента, соответствующая трансляционной диффузии, даетD=(2.9±0.3)·108 см2/с, тогда как внутреннее движение соответствует коэффициенту диффузииD i=(11.7±0.3)·108 см2/с с временем внутренней релаксации τi=(850±200)μmkc.
    Notes: Summary An apparatus for dynamic light scattering (DLS) from solutions has been assembled and tested. The technique of DLS appears as a powerful help towards the understanding of the conformation and the dynamics of macromolecules. In the present work circular DNA, PACL29, of 5400 base pairs (molecular weight≃3.27·106 daltons), has been investigated and two components of the diffusion coefficient (D) have been separated. The first corresponding to translational diffusion givesD=(2.9±0.3)·108cm2/s whereas the internal motion corresponds to a diffusion coefficientD i=(11.7±0.3)·108cm2/s with an internal relaxation time τi=(850±200)μs.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 6 (1985), S. 593-608 
    ISSN: 0392-6737
    Keywords: Chemical thermodynamics ; Molecular biophysics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto In questo lavoro è stata studiata l'interazione fra bromuro di etidio (EB) e DNA in soluzione acqua-metanolo a varie temperature. Si è trovato che l'energia libera di Gibbs associata al legame DNA-EB può essere ben descritta da una relazione lineare nella costante dielettrica della soluzione, come visto anche per altri alcoli. Il ruolo dell'entalpia e dell'entropia di legame è piú semplice se queste quantità sono ricavate isodielettricamente (ε = costance). Con questa procedura, inoltre, è possibile separare le proprietà del solvente dalle caratteristiche del legame DNA-EB mostrando con chiarezza la presenza d'interazioni idrofobiche.
    Abstract: Резюме Исследуется взаимодействие ДНК с бромистым этидием (EB) в присутствии метанола ири различных температурах. Найдено, что свободная энергия Гиббса в случае связи ДНК-ЕВ линейно зависит от диэлектрической постоянной раствора. Указанное свойство обнаружено и для других спиртов. При рассмотрении энтальпии и энтропии в случае связи ДНК-ЕВ установлено, что их роль становится довольно простой, если их изменение осушествляется изодиэлектрически (ε=const). С помощью этой методики можно отличитя свойства, обусловленные растворителем, от свойств, овусловлениых взаимодействием ДНК и ЕВ. Таким образом, можно установить наличие гидрофобного взаимодействия.
    Notes: Summary The interaction of DNA with the dye ethidium bromide (EB) has been investigated under the presence of methanol at varying temperatures. The Gibbs free energy associated with the DNA-EB binding is found to be well described by its linear dependence upon the dielectric constant of the solution, a property also found for other alcohols. When the enthalpy and entropy associated with the binding are considered, it is found that their role becomes rather simple if their evaluation is performed isodielectrically (ε=const). According to this procedure, the varying properties of the solvent can be separated from those of the interacting DNA and EB and the presence of hydrophobic interactions becomes then well established.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 6 (1985), S. 618-630 
    ISSN: 0392-6737
    Keywords: Chemical thermodynamics ; Molecular biophysics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è studiata la denaturazione isoterma del DNA da timo di vitello indotta dalla presenza di quattro alcoli semplici in soluzione. Sono state eseguite sia misure a 67.2 °C, temperatura alla quale la frazione denaturata senza alcoli vale circa 20%, che profili di ≪fusione≫ a temperature variabili. I risultati mostrano che, al crescere della concentrazione e del gruppo alchilico degli alcoli la denaturazione dapprima raggiunge un valore massimo e poi torna indietro. Questo comportamento, attribuito alle proprietà ≪insolite≫ dell'acqua come risulta anche da misure di compressibilità indica che gli effetti idrofobici ed elettrostatici intervengono in modo complicato.
    Abstract: Резюме Исследуется изотермическая денатурация DNA тимуса, индуцированная наличием моногидридных спиртов в растворе. Измерения проводятся при температуре 67.2 °C, при которой денатурация в присутствии спиртов составляет около 20%. Также регистрируются профили плавления при различных температурах. Полученные результаты показывают, что при увеличении концентрации мума, а затем убывает. Это поведение, приписываемое свойствам ≪необыкновенной≫ воды, что получено также из измерений сжимаемости, указывает, что гидрофобные и электростатические эффекты связаны сложным образом.
    Notes: Summary The isothermal denaturation of calf thymus DNA, induced by the presence of some monohydric alcohols in the solution, was investigated. Measurements were performed at a temperature (67.2°C) at which the denaturation, in the absence of alcohols, is about 20% and melting profiles at varying temperatures were also recorded. Results show that with increasing alcohol concentration and alkyl group size DNA denaturation first reaches a maximum and then falls back. This behaviour, ascribed to «unusual» water properties as inferred also from compressibility measurements, indicates that hydrophobic and electrostatic effects are connected in a complex way.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 1065-1074 
    ISSN: 0392-6737
    Keywords: Chemical thermodynamics ; Molecular biophysics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La determinazione delle costanti di equilibrio, come risulta per esempio dalla nota rappresentazione di Scatchard, può essere fortemente errata poiché il valore della risposta del ligando è spesso affetto da grande incertezza. Una causa frequente di questa incertezza deriva dall'uso di campioni che contengono piccole quantità di ligando libero oppure dalla dialisi di equilibrio che è spesso alterata dall'effetto Donnan, perdite di ligando, ecc. Da un'analisi di questo problema si ricava qui un metodo semplice che, nonostante gl'inconvenienti di cui sopra, permette di determinare con grande precisione i parametri di equilibrio.
    Abstract: Резюме Определение постоянныш равновесия может окаться ненадежным, так как обычно величины отклика литандов известны отклика литандов известны с большой неопределенностью. Общая причина этой неопределенности связана с использованием образцов, которые содержат малое количество свободных лигандов, или с равновесным диализом, который обычно родвергается влиянию эффекта Доннана, потерям красителя и др. Из анализа этой проблемы предлагается простая процедура, которая позволяет получить рараметры равновесия с большей точностью.
    Notes: Summary The determination of equilibrium constants, seen,e.g., in the usual Scatchard plots, may be highly inaccurate because generally the values of the bound-ligand response are known with large uncertainty. A common cause of this inaccuracy stems from the use of samples that contain small amounts of free ligand, hardly avoided, or from equilibrium dialysis which is generally affected by the Donnan effect, dye losses, etc. From an analysis of this problem a simple procedure is derived here, so that, in spite of the above drawbacks, the equilibrium parameters can be obtained with better precision.
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  • 6
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Serological studies have demonstrated that lichen ruber planus is associated with the HLA-DR1 antigen. This association was also confirmed by us in the Sardinian population. To establish which DRB1 molecular alleles are involved, we studied a selected group of 14 DR1 positive patients affected by cutaneous idiopathic lichen planus and a group of DR1 positive healthy controls using PCR with sequence-specific primers (PCR-SSP).Comparisons between the allele frequencies in patients and controls showed a positive association with cutaneous idiopathic lichen planus for the DRB 1*0101 allele (RR = 5.8, P= 0.0097). DRB1*0101 and DRB1*0102 are associated with the same DQA1 and DQB1 alleles and are different only for two amino acids in positions 85 and 86 of the DRB 1 gene. In our case report predisposition to cutaneous idiopathic lichen planus is correlated with a valine in position 85 and a glycine in position 86 at the second exon of the DRB 1 gene.
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 685 (1982), S. 123-128 
    ISSN: 0005-2736
    Keywords: (Liver plasma membrane) ; Bilitranslocase ; Liposome ; Organic anion uptake ; Sulfobromophthalein-binding protein
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 856 (1986), S. 1-10 
    ISSN: 0005-2736
    Keywords: Bilitranslocase ; Organic anion transport ; Plasma membrane vesicle ; Sulfobromophthalein
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0005-2736
    Keywords: (Rat liver) ; Bilitranslocase ; Electrogenic transport ; Plasma membrane ; Sulfobromophthalein
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 27 (1966), S. 943-946 
    ISSN: 0022-3697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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