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All relevant data are within the paper and its Supporting Information files. Abstract UVA radiation — nm is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers.
This leads to the production of reactive oxygen species ROSsuch as singlet oxygen 1O2 and hydrogen peroxide H2O2which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids.
We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing.
The time of recovery post irradiation for each of these events can last from few minutes reduction of oxidized RRM1 to several hours replication fork velocity and origin firing.
The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing.
Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen.
The primary cytotoxic effects of UVA radiation are due to the production of reactive oxygen species ROS by photosensitization. This process is initiated by the absorption of UVA photons by various endogenous e. There are two major pathways for photosensitization: Type I and Type II [ 6 ].
In the Type II reaction, the excited photosensitizer transfers its energy to the ground state of 3O2 leading to the formation of singlet oxygen 1O2.
DNA replication is required for faithful inheritance of the genome at each cell division. It starts by recognition of the replication origins by the ORC complex, which is composed of six proteins Orc1 to Orc6 [ 11 ]. The binding of ORC complex to the origins allows the recruitment, during late mitosis and early G1, of the replication initiators Cdc6 Cell division cycle 6 and Cdt1 Chromatin licensing and DNA replication factor 1which facilitates the binding of the core of the replicative DNA helicase Mcm in an inactive form reviewed in [ 12 — 14 ].
The current model is that firing factors are recruited to a subset of licensed origins leading to their activation, then are recycled on other licensed origins, which are in turn fired, and so on, throughout S-phase, until completion of DNA replication [ 19 ].
Thus, regulation of the S phase program occurs at several stages, affecting origin firing, fork velocity, and fork stability. The replication forks elongation requires the incorporation of the deoxyribonucleotide triphosphates dNTPs by the replicative DNA polymerases.
The ribonucleotide reductase RNRor ribonucleotide diphosphate reductase rNDP reductasecatalyses the first reaction committed to DNA synthesis, and is involved in the de novo synthesis of the four dNTPs [ 2425 ]. Therefore, the activity of RNR has to be finely regulated to maintain the steady-state level of the intracellular pool of dNTPs or to adjust it if necessary [ 2526 ].
Moreover, while in yeast, the pool of dNTPs increases significantly in response to DNA damage, it remains almost unchanged in mammals [ 27 ]. The RNR is a heterotetramer composed of two large and two small subunits.IFU method number 8: Determination of soluble solids One of the most common tests conducted in the juice manufacturing industry is the measurement of soluble solids by refractometry.
It is not only used for the assessment of a quality parameter but it is also commercially important where used in . Sucrose and total sugar concentration were significantly different among all phenotypes.
Soluble solids concentration (SSC) was high in su and se compared to the lower SSC of sh 2. Early, mature, and late harvested samples differed in sucrose and total sugar content.
Determination of firmness and soluble solids content. The pear pulp firmness was measured with a GY-3 fruit penetrometer (Sundoo Instruments, Zhejiang, China) with an 8-mm-diameter penetrometer tip.
Before measuring the tissue firmness, a peeler was used to remove the peel in the equatorial region of pear to a depth of about 2 mm. An even force was applied to the penetrometer tip to penetrate the . A. Clean the instrument after each use with distilled water.
Dry with a soft tissue (Kimwipe).
B. Calibrate with a drop of distilled water. Adjust reading to 0 oBrix if necessary with the small set-screw on the back. Verify accuracy with a drop of 5 or 10% sucrose solution (5 grams sugar in mls of distilled water).
Objective To determine soluble solid concentration in some fruits including tropical and temperate fruits by using handheld refractometer. Introduction “Sugar are the major soluble in fruits juices and estimate of sweetness. Other soluble materials include organic and amino acids, soluble pectins, and others.
Soluble solids concentration (SSC) was high in su and se compared to the lower SSC of sh 2. Early, mature, and late harvested samples differed in sucrose and total sugar content. Early, mature, and late harvested samples differed in .