Disinfectants kill microbes but also form by-products with potential health effects

75 Pages·2017·18.94 MB·English

ACS in Philly:
Look inside for a
C&EN-curated guide to
chemistry’s big meeting
and the final program
P.24, 40
AUGUST 1, 2016
WWhhaatt’’ss iinn
tthhee ppooooll??
Disinfectants kill microbes
but also form by-products
with potential health effects
P.28

Contents
VOLUME 94, NUMBER 31
August 1, 2016
Features
Cover story
24 Your guide to the
ACS national meeting
What lies beneath
in Philly
C&EN’s curated list of things to
Urine, sweat, and personal care products do, people to see, and science to
all react with treated pool water to form learn.
chemical by-products, but the jury is
still out on whether those by-products
are harmful to your health.
Page 28
16 New materials take
a bite out of tooth decay
Mercury and gold give way to
polymer composites, alternative
cavity treatments, and new
tooth replacement materials.
26 Career ladder:
21 A biotech hub Joan Frye
grows in Doylestown Science fi ction inspires physical
Pennsylvania center thrives on chemistry professor turned NSF
local talent but struggles to program director.
accommodate demand.
Quote of the week Departments
“Our plan is to 2 Reactions 68 C&ENjobs
3 Concentrates 72 Newscripts
build this into a
biotech corridor
ACS News
like Kendall
Square.” 34 ACS Comment 40 252nd ACS
36 ACS goes abroad National Meeting
—Timothy Block, president, C&EN takes a look at the Events and activities as well as
Pennsylvania Biotechnology society’s international student exhibitor information for the fall
On the cover Center of Bucks County chapters. meeting in Philadelphia.
Photograph by Shutterstock Page 21 38 Obituaries 67 ACS Career Tips
CENEAR 94 (31) 1–72 • ISSN 0009-2347
Reactions
1155—16th St., N.W., Washington, DC 20036
[phone] or [phone]
EDITOR-IN-CHIEF: Bibiana Campos Seijo
MANAGING EDITOR, EDITORIAL: Amanda Yarnell
MANAGING EDITOR, PRODUCTION: Rachel Sheremeta Pepling
B USINESS DEVELOPMENT & PUBLISHER: Kevin A. Davies
▸
SENIOR ADMINISTRATIVE OFFICER: M arvel A. Wills Letters to the editor of “Bretherick’s Handbook of Reactive
BUSINESS Chemical Hazards”; C hem. Health Saf. 2001,
NEW YORK CITY: [phone] Michael McCoy, DOI: 10.1016/s1074-9098(01)00247-7 ; and J.
Assistant Managing Editor, Rick Mullin (Senior Editor), Chemical safety: peroxide
Marc S. Reisch (Senior Correspondent), Alexander H. Tullo (Senior Chem. Educ. 1988, DOI: 1 0.1021/ed065pa226 .
Correspondent), Rachel Eskenazi (Administrative Assistant). formation in isopropanol Svetlana N. Kholuiskaya and
CHICAGO: [phone] Lisa M. Jarvis (Senior Correspondent).
HONG KONG: 852 9093 8445 Jean-François Tremblay (Senior Alexei Y. Metlin
Correspondent). HOUSTON: [phone] Ann M. Thayer (Senior T wo years ago we experienced an explo- N. N. Semenov Institute of Chemical
Correspondent). LONDON: 44 1494 564 316 Alex Scott (Senior Editor).
WEST COAST: [phone] Melody M. Bomgardner (Senior Editor) sion in our lab at the end of isopropanol Physics
distillation. Luckily, it was a small-scale Moscow
POLICY
Cheryl Hogue, Assistant Managing Editor distillation. To elucidate what happened,
Britt E. Erickson (Senior Editor), Jessica Morrison (Associate Powering nuclear power
we prepared several samples of isopropanol
Editor), Andrea L. Widener (Senior Editor)
and kept them on a shelf away from direct
SCIENCE/TECHNOLOGY/EDUCATION
sunlight at room temperature. Jeff Johnson ends his article on the de-
WASHINGTON: Lauren K. Wolf, Assistant Managing Editor
Celia Henry Arnaud (Senior Editor), Stuart A. Borman (Senior Correspondent), We filled transparent glass bottles, tint- commissioning of California’s last nuclear
Matt Davenport (Associate Editor), Stephen K. Ritter (Senior Correspondent).
BERLIN: 49 30 2123 3740 Sarah Everts (Senior Editor). BOSTON: (973) ed glass bottles, and polyethylene bottles power plant, the Diablo Canyon Power
922-0175 Bethany Halford (Senior Editor). CHICAGO: [phone] 75% full with high-purity commercial iso- Plant, with the following statement: “Nu-
Mitch Jacoby (Senior Correspondent). WEST COAST: [phone]
Michael Torrice (Deputy Assistant Managing Editor), [phone] Jyllian propanol. We prepared additional transpar- clear power is carbon-free when generating
Kemsley (Senior Editor), [phone] Elizabeth K. Wilson (Senior Editor) ent glass bottles with the following: electricity; however, it demands significant
JOURNAL NEWS & COMMUNITY:
[phone] Corinna Wu (Senior Editor) a) 97% isopropanol and 3% deionized electricity, carbon-free or otherwise, when
[phone] Jessica H. Marshall (Associate Editor) water. enriching uranium for fuel” ( C&EN, June 27,
ACS NEWS & SPECIAL FEATURES b) Isopropanol refluxed for 1.5 hours with page 15 ). This is true enough, and the energy
Linda Wang (Senior Editor) magnesium chips and a small amount of required for uranium enrichment must be
EDITING & PRODUCTION iodine, followed by distillation; the first 10% included in the energy budget for the life
Kimberly R. Bryson, Assistant Managing Editor of distillate was discarded. cycle of a nuclear power plant.
Craig Bettenhausen (Associate Editor), Taylor C. Hood (Contributing Editor),
Jeff A. Huber (Associate Editor), Manny I. Fox Morone (Associate Editor), c) Isopropanol from sample (b) after ad- However, it is scarcely something unique
Alexandra A. Taylor (Contributing Editor) ditional distillation; fresh 0.3-nm molecular to nuclear power. The corresponding ener-
CREATIVE sieves were added to the final sample to 20% gy cost of a solar electric plant would be the
Robert Bryson, Creative Director by volume. energy expended in the production of the
Tchad K. Blair, Interactive Creative Director
Robin L. Braverman (Senior Art Director), Ty A. Finocchiaro (Senior Web W e replaced the air above the isopro- solar cells used by the plant.
A ssociate), Yang H. Ku (Art Director), William A. Ludwig (Associate Designer) panol every two months by flashing the Evan Appelman
DIGITAL PRODUCTION interior of the bottles with an airstream. State College , Pa.
Renee L. Zerby, Manager, Digital Production
After 24 months, we tested the content of all
Luis A. Carrillo (Web Production Manager), Marielyn Cobero (Digital
Production Associate), Joe Davis (Lead Digital Production Associate), containers for peroxides using the standard
How to reach us
Krystal King (Lead Digital Production Associate), Shelly E. Savage (Senior
iodide method (ASTM International 2008,
Digital Production Associate), Cesar Sosa (Digital Production Associate)
DOI: 10.1520/e0298-08 ).
PRODUCTS MANAGER: Pamela Rigden Snead Chemical & Engineering News
We found peroxides only in sample (b),
CONTENT MARKETING EDITOR: Mitch A. Garcia
Letters to the Editor
which had a peroxide concentration of ap-
SALES & MARKETING ▸ Our e-mail address is [email protected].
S tephanie Holland, Manager, Advertising Sales & Marketing proximately 0.004 mol/L. We suggest that di- ▸ Our fax number is [phone].
Natalia Bokhari (Digital Advertising Operations Manager), Kirsten Dobson isopropyl ether, a well-known peroxidizable ▸ Comments can be left at cen.acs.org.
(Advertising and MarketiMnga rAkesstioncgi aStpe)e,c Siaolnisdtr)a Hadden (Senior Digital substance, formed during refluxing of iso- ▸ Or you can send your letter to:
propanol with magnesium. Diisopropyl ether C&EN Editor-in-Chief
ADVISORY BOARD 1155—16th St., N.W.
Deborah Blum, Raychelle Burks, Kendrew H. Colton, François-Xavier Coudert, boils at 69 °C, which is 14 °C lower than the
Washington, DC 20036
CPatehtelere Nna Cgrluerd, dDeann, PSahuinlae ,T M. Hicahmaeml Sonodfi,a M, Maticthheawel HTaarrsteinllgi,s W, Cilhliraismto Tpohlmera Hni,l l, boiling point of isopropanol, and should be ▸ Letters should generally be 400 words or fewer and
James C. Tung, Jill Venton, Helma Wennemers, Geofrey K. Wyatt removed by distillation. Our results indicate should include the writer’s full name, address, and home
that the first distillation performed without telephone; letters and online comments may be edited
PuTbhloismheads bMy. tChoen A nMellEy RJrI.C, EAxNe cCuHtiEveM DIiCreAcLto Sr O&C CIEEOTY a Vigreux column was not sufficient [sample for purposes of clarity and space. Because of the heavy
Brian D. Crawford, President, Publications Division (b)], while an additional second distillation volume of mail received at C&EN, writers are limited to one
letter in a six-month period.
EDITORIAL BOARD: Nicole S. Sampson (Chair), led to complete removal of all of the formed
ACS Board of Directors Chair: Pat N. Confalone, peroxidizable substance [sample (c)]. Subscriptions
ACS President: Donna J. Nelson, Cynthia J. Burrows, ▸ Send all new and renewal subscriptions and requests
Michael P. Doyle, Jerzy Klosin, Gary B. Schuster Prior to this incident, we were not aware for subscription rates to ACS, Dept. L-0011, Columbus,
Copyright 2016, American Chemical Society that primary and secondary alcohols are OH 43268-0011.
Canadian GST Reg. No. R127571347 peroxidizable. We hope this report is a re- ▸ Changes of address, claims for missing issues, sub-
Volume 94, Number 31 minder to the chemistry community that scription orders, status of records, and accounts should
be directed to Manager, Member & Subscriber Services,
they are and that distillation procedures
ACS, P.O. Box 3337, Columbus, OH 43210; telephone
should take the hazard into account. For [phone] or [phone]; or send an e-mail
more information, see the 7th edition to [email protected].
2 C&EN | CEN.ACS.ORG | AUGUST 1, 2016
Concentrates
▸
Highlights
Tomatoes engineered to travel well, taste better 5
The lifestyle of our single-celled ancestors 6
Snif ng out a new antibiotic 6
Complete amyloid fi brils characterized 7
Chemistry news from the week Tesla spurs demand for lithium chemicals 10
Brexit pondered at European science conference 11
Ag rebound boosts second-quarter results 12
New York requires nail salon ventilation 14
WATER
Legionnaires’ disease outbreaks
tied to Flint water problems
C orrosion in drinking water pipes already experienced outbreaks of Legion-
naires’ disease in June 2014 and May 2015.
allowed deadly bacteria to flourish
The researchers, led by Marc A. Edwards ,
collected tap water samples from homes
The water crisis in Flint, Mich., didn’t just before the city switched back to Detroit wa- and hospitals in and around Flint and de-
poison children with lead; it also likely con- ter in October 2015, the scientists sampled termined Legionella concentrations using
tributed to two outbreaks of Legionnaires’ Flint’s water for L egionella , iron, and free quantitative polymerase chain reaction
disease, according to a new study (E nviron. chlorine. At the time of sampling, Flint had methods. They compared the measure-
Sci. Technol. Lett. 2016, DOI: 1 0.1021/acs. ments to those from baseline U.S. water sur-
Legionnaires’
estlett.6b00192 ). veys that they and the Environmental Pro-
In 2014, Flint stopped taking drinking disease 101 tection Agency carried out in the absence of
water from Detroit and instead started outbreaks and to those from Flint buildings
treating water from the nearby Flint River. that remained on Detroit water.
After this switch, the city’s treatment plant ▸ Cause: Breathing in small droplets of wa- In homes supplied with Flint River
didn’t adequately control the water’s corro- ter containing Legionella bacteria water, the scientists recorded Legionella
siveness, c reating ideal growth conditions ▸ Incidence: 5 ,000 cases per year in the U.S. concentrations roughly seven times as high
for deadly L egionella bacteria. The study is a ▸ Fatality frequency: One in 10 cases as those found in the baseline surveys. The
wake-up call to the many cities failing to ad- ▸ Who’s vulnerable? P eople over 50, smok- team found high levels of iron, 51 ppb, in the
dress corrosion in their aging water pipes, ers, people with chronic lung disease, and Flint homes and hospitals using Flint River
the authors say. people with compromised immune systems water, but found no iron in nearby busi-
Legionnaires’ disease is a deadly pneu- ▸ Symptoms: C ough, shortness of breath, nesses using Detroit water. In more than
N monia caused by inhaling Legionella bac- fever, muscle aches, headaches, and more half the water samples from homes sup-
TIO teria that lurk in the organic matter lining ▸ Common sources of infection: C ontam- plied with the treated Flint River water, the
N
E drinking water pipes. “Lab-scale type inated water in shower stalls, cooling towers researchers could not detect any chlorine.
V
RE studies have illustrated that corrosion in for large air-conditioning systems, decorative No L egionella bacteria were detected in the
P
L & drinking water pipes can stimulate the fountains, and hot tubs buildings using Detroit water.
RO growth of L egionella, ” says A my Pruden , an Source: C enters for Disease Control & Prevention “All this information adds up: The con-
T
ON environmental microbiol- ditions that resulted from the
C
E ogist at Virginia Tech and switch in source water were
S
EA an author of the study. Cor- favorable to growth of Legionel-
DIS rosive water dissolves the la, and because of that, disease
R
O protective mineral lining in cases occurred after the switch,”
F
RS pipes and then leaches iron says Janet E. Stout , director of
E
NT out of old iron pipes. Iron is the Special Pathogens Labora-
E
C a micronutrient that boosts tory in Pittsburgh, the nation’s
RR/ Legionella reproduction. leading L egionella testing lab.
A
C
Y The metal also reacts with “Water operators need to under-
E
N and inactivates chlorine stand that when water service
A
H
E disinfectant that otherwise is disrupted, the risk of Legion-
C
NI would kill the bacteria. naires’ disease can go up and
A
DIT: J tho Tuhgeh Vt cirognindiiati Toencsh in te Falmin t Legionella bacteria tfiheed c,”o smhme cuonnictylu sdheosu. —ld JbAe NnEoTti -
E
CR were ripe for Legionella . So PELLEY, special to C&EN
AUGUST 1, 2016 | CEN.ACS.ORG | C&EN 3
REGISTER NOW
symposium.acs.org
EARLY REGISTRATION ENDS AUGUST 15
Get a discounted registration fee, a membership
to the ACS,and one free student ticket.
Join more than 20 of the world’s leading
researchers for three days of cutting edge science.
Science Concentrates
STRUCTURAL BIOLOGY
Structures of ‘hot’
cancer target solved
CD1 (blue) and CD2 (purple) form an
K nowing HDAC6’s configuration could
ellipsoid complex with pseudo-twofold
help researchers design therapeutics symmetry. The linker (green) connecting
the two domains is on the outside of the
The enzyme HDAC6 is a “sizzling hot target Institute for Biomedical Research and co- complex. Metal ions are gray spheres.
for cancer chemotherapy,” says David W. workers (N at. Chem. Biol. 2016, DOI: 10.1038/ Red arrows indicate the position of the
Christianson , a chemist at the University of nchembio.2140 ). substrate binding cleft in each domain.
Pennsylvania who studies the enzyme. More Unlike other histone deacetylases,
formally known as histone deacetylase 6, HDAC6 has two domains that catalyze ace- tion reaction. They also solved structures
this enzyme is responsible for removing ace- tyl group removal. Catalytic domain 2 (CD2) of HDAC6 with various substrates and
tyl groups from the protein tubulin, a struc- is the main site for deacetylation. Catalytic inhibitors.
tural component of a cell’s inner scaffold. In- domain 1 (CD1), in contrast, is often called Both groups solved structures of the iso-
terfering with this deacetylation process can the “low activity” or “no activity” domain. lated catalytic domains. In addition, Matthi-
disrupt a cell’s ability to divide and transport Christianson and Hai learned that, as’s group solved a structure of CD1 and CD2
nutrients, leading ultimately to cell death. contrary to its nickname, CD1 can be quite linked to one another. Together, the domains
Because researchers would like to dis- active with the right substrate. CD1 has a take on an ellipsoid shape with pseudo-two-
rupt tumor cells this way, they’ve been lysine residue in its binding site where CD2 fold symmetry. “There is a large area of in-
looking for HDAC6 inhibitors as potential has a leucine. Using peptide substrates to teraction between the two domains, with the
cancer treatments. So far, they have needed model segments of tubulin, the researchers linker on the outside,” Matthias says.
to search in the dark without a crystal struc- learned that CD1’s lysine serves as a “gate- Matthias’s team also found that HDAC6
ture to guide them—but not anymore. keeper” that blocks the active site from all gets its specificity for tubulin from a helix
Now two independent groups have substrates except those that have an acetyl- that is oriented differently than in other
solved structures of HDAC6 from zebra- ated lysine at their carboxy terminus. The HDACs and from a flexible tryptophan in a
fish. Christianson and graduate student researchers aren’t yet sure why CD1 has loop connecting two of the enzyme’s helices.
Yang Hai solved one set of crystal struc- that specificity in terms of its regulation of “Both the Matthias and Christianson
tures (N at. Chem. Biol. 2016, DOI: 10.1038/ tubulin, Christianson says. papers determine enzyme-inhibitor
nchembio.2134 ). They also solved one The team, however, was able to get snap- structures useful for pushing therapeutic
structure of human HDAC6, which showed shots of HDAC6’s catalytic mechanism. By discovery forward,” says Karen N. Allen, an
that the zebrafish version is a suitable replacing a histidine in the enzyme’s active enzyme researcher at Boston University.
surrogate. The other set was solved by site, the researchers were able to trap a “These papers are chock-full of important
CELIA ARNAUD
Patrick Matthias of the Friedrich Miescher tetrahedral intermediate of the deacetyla- information.”—
S) FOOD
E
O
T
MA Tasty supermarket tomatoes that can travel
O
T
L. (
O
N
H Most supermarket tomatoes have been bred ing for a pectin lyase enzyme that starts the Craig, which is commonly grown by garden-
C
TE to travel. In other words, they possess a mu- softening process by breaking down com- ers but is too soft to be shipped the global
O
BI tation in a ripening gene that leads to slower plex polysaccharides in tomatoes. Using distances required by the tomato industry.
E
UR fruit softening, thereby allowing the popular RNA interference, they silenced this gene The team found that the transgenic toma-
T
NA produce to be shipped around the world in a flavorful variety of tomato called Ailsa toes did not activate the softening chain re-
E); without getting squished. action, leading to fruits that were travel
R
TU Unfortunately for consumers, that Heirloom (left) and engineered tomatoes. hardy with no consequences to flavor
UC ripening gene also directs flavor and and color (Nat. Biotechnol. 2016, DOI:
R
ST color production. Its mutation blocks 10.1038/nbt.3602).
L. ( these tomatoes from ever fully ripening, Given the public’s concern about
O
M. BI leaving consumers with a relatively bland genetically modified organisms, the dis-
E incarnation of the fruit. covery is unlikely to result in transgenic
H
T. C But there’s hope for tomato lovers, tomato crops. But the work could guide
A
N courtesy of a team led by the University scientists to use conventional breeding
DIT: of Nottingham’s Graham B. Seymour. strategies to grow pectin lyase mutant
E SARAH EVERTS
R The researchers identified a gene cod- varieties. —
C
AUGUST 1, 2016 | CEN.ACS.ORG | C&EN 5
Science Concentrates
NATURAL PRODUCTS
Sniffing out a new antibiotic
A powerful antimicrobial weapon emerges for fighting strains of bacteria that have
become resistant to our existing antibiotic
from the bacterial battle in our noses
arsenal. “It is a new class of antimicrobial,”
he says, “not just another molecule.”
Scientists have long sought novel antibiotics at bay in the other 70% of people. They went Lugdunin killed both methicillin-resis-
by searching for compounds made by bac- looking up our noses for answers. tant S . aureus and vancomycin-resistant
teria living in soils from exotic locales or on Peschel and Krismer’s team discovered enterococci in cell culture tests. The com-
the seafloor. It turns we don’t always have that another S taphylococcus bacterium, S . pound also cleared up S . aureus skin infec-
to go to such extremes. Re- lugdunensis, produces a compound tions in mice when applied topically.
searchers have now found NH that kills S . aureus. The researchers Kim Lewis , a microbiologist at North-
a member of a whole new identified and characterized the eastern University, says Peschel and Kris-
O O
class of antibiotics hiding un- molecule, a novel thiazoli- mer’s work could spur scientists to start
der our noses. The compound, N dine-containing cyclic pep- looking at bacterial fights in our bodies for
H HN
called lugdunin, is a key weapon tide they named lugdunin, new antimicrobial compounds.
O NH O
in the bacterial battle that’s which is the first antibiotic Scientists have long known that S . aureus
HN
raging within our nostrils. to come from a bacterium had a propensity to live in some people’s
Staphylococcus aureus col- NH that lives primarily in noses, Lewis says. “The breakthrough here
H
onizes the nasal passages of N HN people ( Nature 2016, DOI: is that from a set of mundane and well-
O O
about 30% the human population. 10.1038/nature18634 ). known observations they explain why S.
The bacterium bides its time there, S The team started this aureus colonizes only 30% of human noses
looking for chances to spread and wait- project simply to understand and not 100%.”
ing for the opportunity to launch a se- Lugdunin what was happening to bacteria in Peschel and Krismer don’t yet know how
rious infection within its human host. our nostrils, Peschel says. “But it led lugdunin kills bacteria. They have patented
Researchers led by University of Tübingen us to some very unexpected and exciting the compound and are now looking to mine
microbiologists A ndreas Peschel and Bern- findings,” he says, adding that the discovery other human-associated bacteria for novel
BETHANY HALFORD
hard Krismer wondered what keeps S . aureus could lead to the development of new drugs antibiotics. —
ORIGINS OF LIFE
The lifestyle of our
including flavins, S-adenosyl methionine,
and coenzyme A. In fact, this primitive or-
ganism likely lived a pretty similar existence
single-celled ancestors to Clostridia bacteria and archaeal metha-
nogens still living on Earth today.
Martin and his team “have significantly
advanced our understanding of what LUCA
L ast universal common ancestor likely fixed nitrogen did for a living,” comments the University
of Manchester’s James McInerney in an
and relied on hydrogen and carbon dioxide
accompanying perspective (N at. Microbiol.
2016, DOI: 1 0.1038/nmicrobiol.2016.139 ).
Nearly 4 billion years ago, as comets and a heat-loving thermophile that did not re- But, McInerney cautions, it’s important to
asteroids bombarded Earth, occasionally quire oxygen for growth. Instead, the organ- remember that LUCA was not the first form A
A
O
causing the planet’s oceans to vaporize, the ism relied on metals such as iron and nickel of life—just the one to survive the comet N
last universal common ancestor (LUCA) to help it fix nitrogen and carbon dioxide and asteroid bombardments of 4 billion DIT:
SARAH EVERTS E
between bacteria and archaea arose in what using H as an electron donor. LUCA proba- years ago. — R
2 C
was likely a primitive hydrothermal vent. bly harnessed ion gradients for
That’s the conclusion of work by William energy and used many cofactors
Martin and colleagues at Heinrich Heine familiar to biochemists today,
University Düsseldorf. The team analyzed
genomes from current bacteria and archaea The last universal common
species, using bioinformatics to whittle ancestor between bacteria
down 6 million of those organisms’ genes to and archaea probably lived in
a few hundred the team thinks formed the a hydrothermal vent, perhaps
foundation of LUCA’s lifestyle ( Nat. Microbi- similar to the Champagne
ol. 2016, DOI: 10.1038/nmicrobiol.2016.116) . vent (shown) located in
According to this set of genes, LUCA was Japan’s Volcano Islands chain.
6 C&EN | CEN.ACS.ORG | AUGUST 1, 2016
STRUCTURAL BIOLOGY
Complete amyloid
fibrils characterized
S tudies provide atomic-level view of full dimeric
fibrils of key Alzheimer’s-related peptide
The Griffin group’s ribbon representation
Two research teams have independently formation or dissolve fibrils that have al- of the Aβ-42 fibril structure, in rainbow
obtained atomic-resolution structures of ready formed. colors, shows how Aβ-42 peptides align
fully formed amyloid-β peptide fibrils that Robert G. Griffin at Massachusetts In- symmetrically along the dimeric fibril
may be involved in Alzheimer’s disease. stitute of Technology, Sara Linse at Lund axis. Arrows are β-strands, and threads
These fibrils or similar ones form aggre- University, and coworkers carried out one are loops and turns.
gates called “senile plaques” in the brains of the studies (J . Am. Chem. Soc. 2016, DOI:
of patients with the memory- and identi- 10.1021/jacs.6b05129 ). And Anja Böckmann determined last year for an Aβ-42 fibril sub-
ty-loss disease. of the University of Lyon, Beat H. Meier unit—one half of the full dimeric Aβ-42 fi-
The fibrils the teams studied are made and Roland Riek of the Swiss Federal Insti- bril—by Yoshitaka Ishii at the University of
of a 42-amino-acid peptide, Aβ-42, which tute of Technology, Zurich, and cowork- Illinois, Chicago, and coworkers ( Nat. Struct.
is one of two major forms of amyloid-β ers were responsible for the other (P roc. Mol. Biol. 2015, DOI: 10.1038/nsmb.2991;
peptide. It is more neurotoxic, aggregates Natl. Acad. Sci. USA 2016, DOI: 1 0.1073/ C&EN, May 18, 2015, page 6). The three
faster, and is more predominant in senile pnas.1600749113 ). studies thus suggest that the S -shape is a
plaques than the other type, Aβ-40. Sci- “People have waited impatiently for 110 consensus structure for Aβ-42 fibrils.
entists have structurally analyzed Aβ-40 years, since Alois Alzheimer diagnosed his “The new results confirm Ishii’s work
fibrils before. But structural analysis of full first patient, to understand the molecular and also reveal the molecular-level details
Aβ-42 fibrils—thought to be the main bad and structural basis of Alzheimer’s dis- of contacts” between adjacent peptides on
actors in Alzheimer’s disease and therefore ease,” says Shuguang Zhang, also at MIT, the two halves of the fibril, says amyloid
the more important of the two types—has who has studied peptide-fibril formation fibril expert Robert Tycko of the National
been elusive. but wasn’t involved in the recent work. Institute of Diabetes & Digestive & Kidney
Advances in magic-angle spinning nu- The new structures could help researchers Diseases.
clear magnetic resonance spectroscopy identify drugs “to delay or prevent the terri- With the new structures in hand, “There
and laborious efforts to prepare pure fi- ble and devastating disease.” are Avogadro’s number of follow-up exper-
bril samples enabled the teams to almost The studies show that Aβ-42 peptides iments to do,” Griffin says, including study-
simultaneously determine structures of on one side of the dimeric fibril adopt an ing fibrils formed by mutant Aβ-peptides
the full Aβ-42 fibril, which forms as a di- S -shaped conformation and interact hy- that cause early-onset Alzheimer’s disease
mer. The structures could make it easier drophobically with S -shaped peptides ori- and finding agents that bind to Aβ-42. “This
for researchers to design antibodies and ented symmetrically on the other side. The will keep us busy for another decade or
small-molecule drugs that prevent fibril S -shaped structure is essentially the same two,” he says. — STU BORMAN
MATERIALS
Busting a myth about mechanochemical crystallization
Although it may seem counterintuitive Chemists have long thought that using whereas 40 to 60 µL formed polymorph I.
to put a compound into a ball mill to turn one particular liquid when crystallizing Additionally, 10 µL of 1-hexanol, 1-octanol,
it into a crystalline form, the approach compounds via mechanochemical milling or 1-dodecanol formed polymorph III, a
nonetheless works—and adding varying always yields one particular polymorph. polymorph previously only prepared by
amounts of liquid can determine the crys- Seeking to test that dogma, Jones and desolvation.
tal form that results, reports a team led by coworkers crystallized 200 mg of a 1:1 Similar effects could occur for sin-
Bill Jones o f the University of Cambridge equimolar mixture of caffeine and anthra- gle-component crystals, the authors
(C ryst. Growth Des. 2016, DOI: 10.1021/acs. nilic acid using a ball mill, adding from 10 to say. The mechanism behind the phe-
cgd.6b00682). 100 µL of 15 different liquids. nomenon remains to be determined;
C.
O Compounds of interest for materials Four liquids—acetonitrile, nitrometh- the authors suggest that it could be a
S
M. and pharmaceuticals applications often ane, ethylene glycol, and 1,6-hexanediol— result of thermodynamic stabilization of
E
H crystallize into different forms, called formed one polymorph each, regardless of nanoparticles, different growth mech-
C
M. polymorphs. Because polymorphs can have the amount of liquid. The rest of the liquids anisms of the polymorphs, or changes
A
DIT: J. veratriyeisn, gf osrtmabiinligt ya, sspoelucbifiilcit pyo, alynmd oortphher c parno bpe- ydieepldeendd idnigff oenre lniqt upiodl yvmolourmpeh:s 1 o0r t mo 2ix0t uµrLe os,f ipno tlyhme forrepeh-esn cearugsye ddi bffye mreinllcien gb ectownedei-n
E JYLLIAN KEMSLEY
R critically important. ethanol formed polymorph II, for example, tions. —
C
AUGUST 1, 2016 | CEN.ACS.ORG | C&EN 7
Science Concentrates
NANOMATERIALS
PHYSICAL CHEMISTRY Stay weird, gallium
▸
New world champion
base is crowned Gallium has doubled down on its status as a quirky element by showing that it
can support both liquid and solid phases simultaneously over a wide range of
temperatures (Nat. Mater. 2016, DOI: 10.1038/nmat4705). Bulk gallium lique-
By preparing the o-diethynylbenzene dian- fies at 30 °C, the temperature of a warm summer’s day and a melting point
ion in a gas-phase experiment, a research much lower than most metals. Scientists
team in Australia has set a record for the led by April S. Brown of Duke University
world’s strongest chemical base—a record have discovered that gallium nanoparticles
the researchers suggest may be difficult to exhibit another thermal anomaly, existing
ever break (Chem. Sci. 2016, DOI: 10.1039/ as liquid blobs with solid cores from about
c6sc01726f). When it comes to strong acids –90 °C to 525 °C when the particles rest on
and bases, sulfuric rigid, inert sapphire substrates. Within the
– –
acid and sodium nanoparticle, the pressure is sufficiently
hydroxide typically high to crystallize the gallium near the core.
come to mind. These Meanwhile, a balance between surface and Energy-filtered transmission
substances are cer- interfacial forces creates an equilibrium electron microscopy reveals
tainly strong and that favors a liquefied shell. Although the solid cores and liquid
o-Diethynylbenzene corrosive, Berwyck this balance stands up to large changes in shells of gallium nanoparticles
dianion Poad of Queensland temperature, it is upset by changing the on a sapphire substrate.
University of chemical and mechanical properties of the
Technology and coworkers note. But as the substrate, the team shows. For instance, gallium particles formed a single liq-
researchers explain, acid and base strengths uid phase when deposited on reactive silicon substrates or on amorphous, de-
are typically measured by a molecule’s pro- formable glass substrates. Selecting different substrates could give researchers
ton affinity, which is the amount of energy a new dimension of control to tailor the properties of dual-phase nanoparticles
given off when a molecule binds a hydrogen for catalytic systems and optoelectronic devices. —MATT DAVENPORT
ion. By this measure, a hydroxide anion has
the largest proton affinity in aqueous solu-
tion at 1,633 kJ/mol. But in the gas phase, the
strongest base until now was the lithium
monoxide anion, with a proton affinity of
1,782 kJ/mol. To make the new record holder,
Poad and coworkers first used a computa-
tional model to search for multiply charged
anions as the strongest possible bases that
might be stable enough to prepare. With
diethynylbenzene dianions identified as a
target, the researchers developed a process
to make them by sequentially ionizing dicar-
boxylic acid precursors in a mass spectrom-
eter. They show that the o-diethynylbenzene
isomer is the strongest, with a proton affini-
ty of 1,843 kJ/mol, which is enough to depro- S)
R
tonate benzene in the gas phase, and likely Researchers pipette an enzyme solution (top, blue) onto a plastic pillar and allow it to LA
L
any other challenger. —STEVE RITTER concentrate via evaporation. Then they add a sample solution (yellow). Evaporation- PI
driven currents mix the sample, promoting a reaction and producing a color change. TIC
S
A
L
DIAGNOSTICS researchers led by Jose L. Garcia-Cordero orate to concentrate it before adding a glu- M. (P
▸ Fast assays on of National Polytechnic Institute, in Mon- cose solution. When the enzymes acted on HE
C
terrey, Mexico, designed an alternative the glucose, the sugar underwent a set of L.
micropillars approach that exploits rather than pre- reactions to form a colored product. The NA
A
vents evaporation. Evaporation can cause team monitored reactions in both high and H);
P
surface tension differences in a droplet low humidity for 20 minutes, taking pho- A
R
Pipetting tiny droplets on top of mi- that spur Marangoni currents, which re- tographs at intervals. At high humidity, the OG
R
croscale plastic pillars could offer an ad- sult from liquid flowing to areas of higher droplets on the pillars didn’t evaporate MIC
vantage over microwell plates for carrying surface tension. The team used a milling or substantially change color, suggesting R (
out diagnostic assays (Anal. Chem. 2016, machine to fashion 800-µm-diameter, that evaporation provides the mixing ATE
M
DOI: 10.1021/acs.analchem.6b01657). Mix- 1-mm-tall pillars on an acrylic plate. The necessary for the reaction to occur. But as T.
A
ing and sample evaporation are potential researchers then conducted a colorimetric the droplets evaporated at low humidity, N
problems when working with microliter assay by pipetting an enzyme solution their color changed. —MELISSA PANDIKA, DIT:
volumes of samples in microplates. So onto the top of a pillar and letting it evap- special to C&EN RE
C
8 C&EN | CEN.ACS.ORG | AUGUST 1, 2016