Reply to Israel Carmi (2002): “Are the 14C Dates of the Dead Sea Scrolls Affected by Castor Oil Contamination?”

The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

The Effects of Possible Contamination on the Radiocarbon Dating of the Dead Sea Scrolls I: Castor Oil

Some fragments of the Dead Sea Scroll manuscripts were contaminated with castor oil in the late 1950s. We have conducted experiments in order to establish if the AAA pretreatment cleaning procedures conducted on Dead Sea Scroll manuscript samples in the last two dating series were effective in removing oil contamination. Our experiments show that not all oil contamination can be expected to have been removed by the acid-alkaline-acid (AAA) pretreatment, and that the radiocarbon ages previously reported therefore cannot be guaranteed to be correct. Any samples contaminated with castor oil were most likely reported with ages that are too young by an unknown amount.

Qumran Textiles in the Palestine Exploration Fund, London: Radiocarbon Dating Results

Three pieces of fabric from Qumran’s Cave 1 have been stored in the Palestine Exploration Fund collection since the 1960s but have hitherto never been tested or re-examined. The fabric is made of linen, and was probably used for wrapping or packing scrolls, or sealing jars. New radiocarbon dating on one piece of fabric indicated a probability of 55% for it being made between 1 and 55 A.D., and a probability of 95.4% that it was made between 50 cal B.C.–80 cal A.D.

THE EFFECTS OF POSSIBLE CONTAMINATION ON THE RADIOCARBON DATING OF THE DEAD SEA SCROLLS II THE EFFECTS OF POSSIBLE CONTAMINATION ON THE RADIOCARBON DATING OF THE DEAD SEA SCROLLS II: EMPIRICAL METHODS TO REMOVE CASTOR OIL AND SUGGESTIONS FOR THE EFFECTS O

ABSTRACT. While kept at the Rockefeller Museum in East Jerusalem, many Dead Sea Scroll fragments were exposed to castor oil by the original team of editors in the course of cleaning the parchments. Castor oil must be regarded as a serious contaminant in relation to radiocarbon dating. If modern castor oil is present and is not removed prior to dating, the 14 C dates will be skewed artificially towards modern values. In Rasmussen et al

Differential roles of human Dicer-binding proteins TRBP and PACT in small RNA processing

During RNA interference and related gene regulatory pathways, the endonuclease Dicer cleaves precursor RNA molecules to produce microRNAs (miRNAs) and short interfering RNAs (siRNAs). Human cells encode a single Dicer enzyme that can associate with two different double-stranded RNA (dsRNA)-binding proteins, protein activator of PKR (PACT) and trans-activation response RNA-binding protein (TRBP). However, the functional redundancy or differentiation of PACT and TRBP in miRNA and siRNA biogenesis is not well understood. Using a reconstituted system, we show here that PACT and TRBP have distinct effects on Dicer-mediated dsRNA processing. In particular, we found that PACT in complex with Dicer inhibits the processing of pre-siRNA substrates when compared with Dicer and a Dicer–TRBP complex. In addition, PACT and TRBP show non-redundant effects on the production of different-sized miRNAs (isomiRs), which in turn alter target-binding specificities. Experiments using chimeric versions of PACT and TRBP suggest that the two N-terminal RNA-binding domains of each protein confer the observed differences in dsRNA substrate recognition and processing behavior of Dicer–dsRNA-binding protein complexes. These results support the conclusion that in humans, Dicer-associated dsRNA-binding proteins are important regulatory factors that contribute both substrate and cleavage specificity during miRNA and siRNA production

siRNA Repositioning for Guide Strand Selection by Human Dicer Complexes

The human ribonuclease Dicer and its double-stranded RNA (dsRNA) binding protein (dsRBP) partners TRBP and PACT play important roles in the biogenesis of regulatory RNAs. Following dicing, one dsRNA product strand is preferentially assembled into an RNA-Induced Silencing Complex (RISC). The mechanism of strand selection in humans and the possible role of Dicer in this process remains unclear. Here we demonstrate that dsRNAs undergo significant repositioning within Dicer complexes following dicing. This repositioning enables directional binding of RNA duplexes, thereby biasing their orientation for guide strand selection according to the thermodynamic properties of the helix. Our findings indicate that Dicer is itself capable of sensing siRNA thermodynamic asymmetry regardless of the dsRBP to which it is bound. These results support a model in which Dicer employs two distinct RNA binding sites – one for dsRNA processing and the other for sensing of siRNA thermodynamic asymmetry – during RISC loading in humans