Edward P. Richards

Molecular mobilities of soluble components in the aqueous phase of chromaffin granules.

NMR relaxation times have been used to characterize molecular motion and intermolecular complexes in the aqueous phase of bovine chromaffin granules. Partially relaxed 13C and proton spectra have been obtained at 3 and 25 degrees C. T1 measurements of five protonated carbons on epinephrine (C2, C5, C6, CHOH and NCH3) give a correlation time of 0.15 (10(-9)) s at 25 degrees C for the catechol ring and methine carbon, while the effective correlation time for the NCH3 group is somewhat shorter due to its internal degree of rotational freedom. Resonances of protonated carbons on the soluble protein chromogranin give very similar correlation times: 0.20 (10(-9)) s for the peptide alpha-carbon and 0.2 (10(-9)) s for the methylene sidechain carbons of glutamic acid. The correlation time (tauR) of ATP was not measured directly using 13C T1 data due to the weakness of its spectrum, but its reorientation appears to be substantially slower than that of epinephrine or chromogranin. This conclusion is based on three observations: (1) the qualitative temperature dependence of T1 for H2 and H8 on the adenine ring places tauR for ATP to the right of the T1 minimum, or tauR greater than or equal to 1.0 (10(-9)) s; (2) 13C-resonances of ATP have anomalously low amplitudes compared with epinephrine resonances, a fact that is readily explained only if ATP undergoes substantially slower reorientation; and (3) a comparison of the T1 data of H8 in chromaffin granules and in a dilute aqueous solution, where tauR for ATP can be measured directly indicates that tauR approximately 1.0 (10(-9)) s at 25 degrees C in the granules. The relaxation data are consistent with the concept of a storage complex based on electrostatic interactions between a polyion (chromogranin) and its counterions (ATP and epinephrine), in which ATP cross-links cationic sidechains of the protein.

Analysis of the carbon-13 and proton NMR spectra of bovine chromaffin granules

Natural abundance carbon-13 and proton NMR spectra of bovine chromaffin granules have been obtained and analyzed using computer simulation techniques. High resolution spectra show the presence of a fluid aqueous phase containing epinephrine, ATP and a random coil protein. The protein spectrum contains unusually intense resonances due to glutamic acid and proline and has been simulated satisfactorily using the known amino acid composition of chromogranin A. The lipid phase of chromaffin granules gives rise to intense, but very broad, resonances in the carbon-13 spectrum. Protons in the lipid phase are also observable as a very rapid component of the proton-free induction decay (T2 approximately equal to 15 microns). Linewidths of the carbon-13 spectra have been used to set upper limits on rotational correlation times and on the motional anisotropy in the aqueous phase. These limits show that the aqueous phase is a simple solution (not a gel) that is isotropic over regions much larger than solute dimensions. No gel transition is observed between -3 and 25 degrees C. The carbon-13 spectra are definitely inconsistent with a lipoprotein matrix model and chromaffin granules previously proposed by Helle and Serck-Hanssen ((1975) Mol. Cell, Biochem. 6, 127-146). Relative carbon-13 intensities of ATP and epinephrine are not consistent with the known 1 : 4 mol ratio of these components. This fact suggests that epinephrine and ATP are not directly complexed in intact chromaffin granules.

NMR evidence for an acetylcholine ATP complex

Abstract The interaction of acetylcholine with ATP was studied using proton NMR. T 1 measurements indicate the formation of a complex with a probable composition of four (4) acetylcholine molecules for each ATP molecule.

Legal defenses to the use of data digits to identify fabricated data

I the previous article, we explained how the Office of Research Integrity (ORI) at the U.S. Public Health Service (PHS) uses “insignificant” digits in research data to catch researchers falsifying or fabricating data. Basically, ORI assumes that certain digits reported in data are not significant to the measurement they purport to represent. Moreover, ORI assumes that such digits occur in falsified or fabricated data will not be selected randomly. It therefore applies the Chi Square test to the “insignificant” digits in questionable data and estimates the probability that the digits were generated randomly. Where bias is found in digits that should be random, the questionable data are further suspect, and the researcher who reported them may be convicted of scientific misconduct. In applying this theory, ORI assumes that any digit to the right of the leading one that is not distributed randomly in the data raises the possibility that the data are falsified. However, any experimental scientist would intuit that the use of significant digits for this purpose is far less probative evidence that data are fabricated than is the use of truly insignificant digits. In what follows, rather than adopt ORI’s terminology, we refer to a left-most digit as the “most significant digit,” the right-most significant digit as the “least significant digit,” the rest of the significant digits (if any) as “significant digits,” and any other digits in a datum as “insignificant digits.”

Legal considerations in screening pregnant women for human immunodeficiency virus

This article examines the legal implications of studies showing that the probability of maternal-to-infant human immunodeficiency virus transmission can be reduced by physician interventions. These interventions require knowledge of a pregnant womans human immunodeficiency status. Hence the offering of human immunodeficiency virus testing has become a standard of care in pregnancy. This standard of care is examined with respect to the following: (1) the physicians legal duty to the infant, (2) negligence for failing to test, (3) liability when testing only reduces the probability of transmission, (4) damages, (5) informing women about the results of their testing, (6) protecting against liability, and (7) dealing with human immunodeficiency virus-infected pregnant women. It is concluded that the physicians are likely to have legal difficulties if a human immunodeficiency virus-infected baby is born to a woman who was not offered testing or if testing is done without documenting consent. Suggestions are made for reducing liability when testing is done, when patients refuse testing, and when one is caring for human immunodeficiency virus-infected women.

Engineering and the law. Science in the Supreme Court: round two

Since the United States Supreme Courts 1993 decision in the Daubert case, federal judges have been looking more carefully at the scientific basis of the expert testimony presented in their courtrooms. Medical-device litigation, especially that over the alleged harm caused by breast implants, has been at the center of this rethinking of the role of the court in assessing scientific evidence. Cases that were about to settle for a total of more than

Keeping junk science out of the courtroom

4 billion are now being seen as potentially groundless. One judge in Oregon dismissed a group of breast-implant cases. Finding there was no scientific basis for the plaintiffs claims. Another court, overseeing a large group of cases, has appointed an independent panel of experts to determine if the plaintiffs experts will be allowed to testify. As in the Oregon breast-implant cases, the exclusion of a plaintiffs expert witness often means the court must also dismiss the plaintiffs case. Plaintiffs have appealed these decisions, arguing that since the trial courts exclusion of their experts testimony ends their case, the appeals courts should strictly review the correctness of the trial courts decision. In GE vs. Joiner, decided December 1997, the United States Supreme Court established the proper standard for appellate review of decisions by trial courts to exclude evidence.

Engineering and the law. The Supreme Court rules on medical device liability-or does it?

Junk science gets into the courtroom in the guise of an expert witness who is called by a party to give an opinion about a technical matter on behalf of the party who called the expert. Attorneys take advantage of the fact that judges lack the background, or sometimes the will, to keep junk science out. We propose some new rules, which, if adopted, would help keep junk science out of the courtroom.

When are expert witnesses liable for their malpractice

In previous articles the author has discussed the evolution of federal preemption for state products-liability claims against medical-device manufacturers. This is a controversial approach, and federal district and appeals courts have made opposing rulings on cases that are legally identical. Some courts have refused to allow any products-liability claims for devices, some have limited claims against only some devices, and some courts refused to limit claims in any cases. The United States Supreme Court has now reviewed this law to resolve the conflicts between the lower courts. The Court rendered its decision in Medtronic, Inc., v. Lora Lohr, 116 S.Ct. 2240, June 26, 1996. The Court did not find preemption in the case it reviewed, but neither did it clearly eliminate the chance of preemption in other cases. Ruling in a split decision, it assured that confusion will still reign.

Engineering and the law-how is an anesthesia machine like a lawnmower? The problem of the learned intermediary

Expert witness testimony is essential to all legal proceedings that involve technical, medical, professional, or scientific matters. More generally, experts must testify whenever the underlying matters are beyond the common knowledge of lay jurors. As we have written in previous articles, the courts have spent much time and energy determining how to access the proper qualifications for experts. Without an expert, a plaintiff cannot proceed to trial, and a defendant is usually doomed to an adverse jury verdict. Since experts are often a scarce resource that is essential to litigation, many charge substantial fees for their services. If the expert does not do a good job, the party employing the expert will lose the lawsuit as well as be responsible for the experts fees. This article deals with expert witness malpractice. Should the party hiring the expert be entitled to sue the expert for malpractice? Should the party that the expert testifies against be allowed to sue the expert? Conversely, what are the legal risks of being an expert witness?.