A new class of amphiphiles bearing rigid hydrophobic groups for solubilization and stabilization of membrane proteins

Article abstract of DOI:10.1002/chem.201200069

Non-traditional amphiphiles: Conferring aqueous solubility on membrane proteins generally requires the use of a detergent or other amphiphilic agent. A new class of amphiphiles was synthesized, based on steroidal lipophilic groups, and evaluated with several membrane proteins. The results show that the new amphiphile, glyco-diosgenin (GDN; see figure), confers enhanced stability to a variety of membrane proteins in solution relative to popular conventional detergents, such as dodecylmaltoside (DDM). Copyright

Full text of DOI:10.1002/chem.201200069

COMMUNICATION
DOI: 10.1002/chem.201200069
A New Class of Amphiphiles Bearing Rigid Hydrophobic Groups for
Solubilization and Stabilization of Membrane Proteins
Pil Seok Chae,*[a] Søren G. F. Rasmussen,[c] Rohini R. Rana,[d] Kamil Gotfryd,[e]
Andrew C. Kruse,[c] Aashish Manglik,[c] Kyung Ho Cho,[a] Shailika Nurva,[f]
Ulrik Gether,[e] Lan Guan,*[f] Claus J. Loland,*[e] Bernadette Byrne,*[d]
Brian K. Kobilka,*[c] and Samuel H. Gellman*[b]
Integral membrane proteins (IMPs) are crucial cellular
components, mediating the transfer of material and signals
between the environment and the cytoplasm, or between
different cellular compartments. Structural and functional
analysis of IMPs is important; more than half of current
pharmaceutical agents target proteins in this class.[1] IMP
characterization is often challenging, and sometimes impos-
sible, because of difficulties associated with handling these
macromolecules.[2] IMPs in the native state display large hy-
drophobic surfaces, which are not compatible with an aque-
ous environment; therefore, detergents are required to ex-
tract IMPs from the lipid bilayer and to maintain the native
state of the protein in solution.[3] Nonionic detergents, such
as dodecyl-b-d-maltoside (DDM) and octyl-b-d-glucoside
(OG), are generally preferred for these applications. Despite
the comparatively mild nature of DDM, OG and related de-
tergents, many membrane proteins denature and/or aggre-
gate upon solubilization with these agents.[4]
Diverse strategies have been pursued to develop new
tools for solubilization of IMPs from membranes and for
maintenance of these proteins in a native-like state in aque-
ous solution. Techniques that are effective for solubilization
are not always optimal for stabilization, and vice versa.
These efforts have included exploration of novel amphiphil-
ic molecules that depart from traditional detergent architec-
tures.[5] Specifically tailored amphiphiles that facilitate IMP
crystallization are particularly noteworthy.[5l,m,6] Amphiphilic
polymers (“amphipols”)[7] and discoidal lipid bilayers stabi-
lized by an amphiphilic protein scaffold (“nanodiscs”)[8] rep-
resent highly innovative approaches for stabilizing IMPs in
native-like states in aqueous solution. It is not clear, howev-
er, whether these approaches can support growth of high-
quality crystals for diffraction analysis. Furthermore, neither
amphipols nor nanodiscs were designed to extract IMPs
from biological membranes. Despite considerable progress
in the development of new compounds and strategies for
membrane protein solubilization and stabilization, new tools
are needed, because many IMPs are currently refractory.
Given the great variation in structure and physical proper-
ties among membrane proteins, it is very unlikely that
a single amphiphile or amphiphile family will be optimal for
every system, or even most systems, and exploration of new
amphiphilic agents is therefore important for membrane
protein biochemistry. Herein we report a class of structurally
novel amphiphiles that display favorable behavior, relative
to traditional detergents such as DDM, toward a diverse set
of membrane proteins.
[a] Prof. P. S. Chae, K. H. Cho
Department of Bionano Engineering, Hanyang University
Ansan, 426-791 (Korea)
E-mail: pchae@hanyang.ac.kr
[b] Prof. S. H. Gellman
Department of Chemistry, University of Wisconsin-Madison
1101 University Avenue, Madison, WI 53706 (USA)
E-mail: gellman@wisc.edu
[c] Prof. S. G. F. Rasmussen, A. C. Kruse, A. Manglik,
Prof. B. K. Kobilka
Molecular and Cellular Physiology, Stanford University
Stanford, CA 94305 (USA)
E-mail: kobilka@stanford.edu
[d] R. R. Rana, Dr. B. Byrne
Department of Life Sciences, Imperial College London
London, SW7 2AZ (UK)
E-mail: b.byrne@imperial.ac.uk
[e] K. Gotfryd, Prof. U. Gether, Prof. C. J. Loland
Department of Neuroscience and Pharmacology
University of Copenhagen
2200 Copenhagen (Denmark)
The new amphiphiles (Figure 1) all contain a rigid, ste-
roid-based lipophilic group and a di-maltose hydrophilic
group. Three of the new compounds are derived from litho-
cholic acid and are therefore designated “glyco-lithocholate”
amphiphiles (GLC-1, GLC-2 and GLC-3); the fourth is de-
rived from diosgenin and designated “glyco-diosgenin”
(GDN). Many previously reported amphiphiles based on
steroidal skeletons have been derivatives of cholic acid or
deoxycholic acid, including members of the widely-used
E-mail: cllo@sund.ku.dk
[f] S. Nurva, Prof. L. Guan
Department of Cell Physiology and Molecular Biophysics
Texas Tech University Health Sciences Center
Lubbock, TX 79430 (USA)
E-mail: lan.guan@ttuhsc.edu
Supporting information for this article (including synthesis and char-
acterization of amphiphiles, detergent screening, and stabilization
measurements) is available on the WWW under http://dx.doi.org/
10.1002/chem.201200069.
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brane with a conventional de-
tergent and then assessed for
stability after introduction of
one of the new amphiphiles as
the predominant solubilizing
agent. Favorable outcomes of
these initial studies led us to
evaluate the new agents for
membrane-extraction capabili-
ties; GDN proved to be partic-
ularly effective in this context.
The four new compounds
were easily prepared on
a multi-gram scale, as is neces-
sary if they are to serve as re-
search tools (see the Supporting
Information). All four are
highly soluble and display fairly
low critical micelle concentra-
tions (CMC; determined by flu-
orescent dye solubilization,[10]
Table 1). These values are
somewhat smaller than the
CMC of DDM, which indicates
a strong tendency of the new
agents to self-assemble. Table 1
provides the hydrodynamic
radius (Rh) of the micelles
formed by each amphiphile, as
determined by dynamic light
scattering (DLS). The micelles
formed by GLC amphiphiles
are slightly smaller than those
Figure 1. Chemical structures of new amphiphiles (GLC-1, GLC-2, GLC-3 and GDN).
CHAPS family, cholate-based facial amphiphiles, and
tandem-facial amphiphiles.[5a,h,k] In these cases the rigid ster-
oidal units are facially amphiphilic:[9] one side is hydrophilic,
displaying either hydroxyl groups or carbohydrate units. In
contrast, the hydrophobic units in the GLC and GDN am-
phiphiles introduced here are hydrophobic on both faces,
and the hydrophilic moiety is appended to the periphery of
the rigid hydrophobic unit. A cholesterol-based amphiphile,
“chobimalt,”[5n] was recently described. This compound
bears a linear tetrasaccharide that is structurally different
from and less synthetically accessible than the di-maltose
unit of the GLC and GDN amphiphiles. The capabilities of
chobimalt have been assessed with only a single IMP so far,
the human kappa opioid receptor type 1 (hKOR1), and the
results were less promising than the findings we report for
the new GLC and GDN amphiphiles. hKOR1 could not be
extracted in an active form from a biological membrane
with chobimalt alone; however, use of chobimalt as an addi-
tive to stabilize DDM-solubilized hKOR1 was successful.
The studies described below involve multiple membrane
proteins from various structural classes, to assess the poten-
tial of the GLC and GDN amphiphiles for broad utility. Ini-
formed by DDM, while the micelles formed by GDN are
slightly larger.
Table 1. Critical micelle concentration (CMC) of GLC/GDN amphi-
philes and hydrodynamic radii (Rh) of their micelles (MeanÆSD, n=5).
[a]
Mw
CMC
[mM]
CMC
A
Rh
[nm][b]
GLC-1
GLC-2
GLC-3
GDN
1112.3
1127.3
1083.3
1165.3
510.1
ꢀ52
ꢀ0.0060
ꢀ0.00090
ꢀ0.00077
ꢀ0.0021
ꢀ0.0087
3.22Æ0.03
3.32Æ0.04
3.27Æ0.08
3.86Æ0.05
3.42Æ0.03
ꢀ8.0
ꢀ7.1
ꢀ18
DDM
ꢀ170
[a] Molecular weight of detergents. [b] Hydrodynamic radius of micelles
measured by dynamic light scattering.
To assess the potential utility of new amphiphiles as tools
for IMP manipulation, multiple protein systems must be ex-
amined. We used DDM as a benchmark for conventional
detergent performance in each case, because DDM is proba-
bly the most commonly employed amphiphilic agent in
membrane protein research. We focused initially on bacter-
iorhodopsin (bR), which has been commonly used for evalu-
ation of novel amphiphiles because stability can be assessed
conveniently via spectrophotometry.[5b,c] bR was extracted
tial experiments involved
a conservative experimental
design, in which IMPs were first extracted from the mem-
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from the native purple membrane with 2.0 wt% octyl-b-d-
thioglucoside (OTG),[11] and following ultracentrifugation to
remove insoluble debris, the bR solution was diluted with
amphiphile solutions to give 0.2 wt% OTG+1.6 wt% new
agent or DDM. The absorbance of the solutions at 554 nm
was measured periodically over 20 days. Figure 2a shows
that two new agents, GLC-2 and GDN, are more effective
than conventional detergents OTG and DDM at maintain-
ing the native structure (see the Supporting Information,
Figure S1 for results with other agents). GDN was the best
of the new agents, showing negligible loss in protein integri-
ty after 20 days. When we conducted the assay at a lower
amphiphile concentration, 0.2 wt% OTG+0.8 wt% new
agent or DDM, similar results were obtained (see the Sup-
porting Information, Figure S1).
The promising behavior manifested by GDN in terms of
the stability of bR and the R. capsulatus superassembly
prompted us to examine this amphiphile with the murine cy-
tidine-5’-monophosphate-sialic acid transporter (CMP-
Sia).[13] The protein was initially extracted from Saccharomy-
ces cerevisiae membranes with 1% DDM and isolated in
buffer containing 0.03% DDM. The final purified protein
(6 mgmLÀ1) was diluted 1:100 into solutions containing
DDM or GDN at 0.042 wt% (which corresponds to CMC+
0.033 wt% for DDM and CMC + 0.040 wt% for GDN).
The DDM- and GDN-solubilized CMP-Sia were analyzed
by gel filtration before and after incubation for 2 h at 308C
(Figure 3a and b). The results show GDN to be superior to
DDM: CMP-Sia solubilized with DDM displays approxi-
mately 50% integrity after the 2 h period, whereas GDN-
solubilized protein retains more than 90% integrity. The fa-
vorable effect of GDN on CMP-Sia stability was further
supported by N-[4-(7-diethylamino-4-methyl-3-coumarinyl)
phenyl]maleimide (CPM) assay results when we evaluated
the detergents at CMC+0.04 wt% (see the Supporting In-
formation, Figure S3a).[14] Two other membrane proteins
were examined with the CPM assay: the rhomboid intra-
membrane serine protease GlpG[15] and the succinate:qui-
none oxidoreductase (SQR),[16] both of which were ex-
pressed in Escherichia coli. In both cases, the results suggest
that the new GLC/GDN amphiphiles are superior to DDM
at maintaining the native structure (see the Supporting In-
formation, Figure S3b and c).
Figure 2. Stability of a) bacteriorhodopsin (bR) and b) R. capsulatus
LHI-RC superassembly at RT as a function of time. Agents were tested
at 0.2 wt% OTG+1.6 wt% amphiphile for bR and at CMC+0.04 wt%
&
*
for the R. capuslatus superassembly. Key: GLC-2 ( ); GDN ( ); OTG
^
*
(
); DDM (&); OG ( ).
We turned next to a more challenging system, the photo-
synthetic superassembly from Rhodobacter capsulatus,[12]
which contains the light harvesting I (LHI) complex and the
reaction center (RC) complex. This superassembly contains
more than 30 protein molecules; the integrity of which can
be assessed based on the 875 nm/680 nm absorbance ratio.[5i]
The superassembly was extracted from the native membrane
with 1.0 wt% DDM and purified with DDM at its CMC
(0.009 wt%). This preparation was diluted with solutions
containing new agents, so that residual DDM (0.0004 wt%)
was far below its CMC. The final concentration of each
agent was CMC+0.04 wt%. Figure 2b shows that the LHI-
RC superassembly is substantially more stable over 20 days
when solubilized by GLC-2 or GDN relative to solubiliza-
tion with DDM or OG. Similar results were obtained with
different detergent concentrations (see the Supporting Infor-
mation, Figure S2).
Figure 3. a, b) Gel filtration analysis for CMP-Sia and c) time course ac-
tivity of LeuT (scintillation proximity assay (SPA), based on [3H]-Leu
binding). Gel filtration analysis was performed at a detergent concentra-
tion of 0.042 wt%, before or after incubation of solubilized CMP-Sia at
308C for 2 h. SPA was conducted with detergents at CMC+0.04 wt% or
CMC+0.2 wt% with LeuT stored at RT. Results are expressed as% ac-
tivity relative to the day 0 measurements (meanÆs.e.m., n=2).
The new amphiphiles were evaluated for the ability to
maintain the leucine transporter (LeuT) from Aquifex aeoli-
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P. S. Chae, L. Guan, C. J. Loland, B. Byrne, B. K. Kobilka, S. H. Gellman et al.
cus in a functional state.[17] The transporter was initially ex-
In the examples discussed so far, conventional detergents
such as DDM were used to extract IMPs from the mem-
brane, and then in most cases the solution of detergent-solu-
bilized protein was diluted with amphiphile-containing solu-
tions to evaluate the new agents. With this approach it is
possible that the small amount of residual conventional de-
tergent could affect the protein stability. To exclude this pos-
sibility, GLC-3 and GDN were used to extract wild-type
b2AR (b2AR WT)[19] from the membrane. Receptor activity
was measured by using a binding assay involving the antago-
nist [3H]-dihydroalprenolol. The DDM-solubilized receptor
showed low initial activity and rapidly decomposed (Fig-
ure 4b). GLC-3-solubilized receptor showed initial activity
similar to that of DDM-solubilized receptor, but in this case
activity was maintained over 72 h. GDN-solubilized b2AR
WT showed remarkable behavior: high initial activity (>3-
fold increase relative to that seen with DDM) that did not
vary over 72 h.
We next turned to a d-opioid receptor-T4L fusion (dOR-
T4L), another GPCR, to compare GDN with the recently
reported amphiphile MNG-3,[5l] which has proven to be es-
sential for crystallization of several other GPCR con-
structs.[6] Consistent with prior observations, MNG-3-solubi-
lized dOR-T4L showed higher activity than DDM-solubi-
lized dOR-T4L (see the Supporting Information, Figure S5).
Remarkably, GDN-solubilized dOR-T4L displayed even
higher activity. Thus, GDN seems to be very promising for
further GPCR solubilization efforts.
tracted with DDM and then diluted with amphiphile-con-
taining solutions to generate an amphiphile concentration of
CMC+0.04 wt% or CMC+0.2 wt%. At both concentra-
tions, GDN was very effective at maintaining LeuT activity,
as indicated by binding of radiolabeled leucine, with preser-
vation of more than 95% of initial activity after 12 days
(Figure 3c). In contrast, DDM-solubilized LeuT lost activity
over this period. The GLC amphiphiles were also superior
to DDM in terms of maintaining LeuT activity, although
they did not match GDN (see the Supporting Information,
Figure S4).
To assess the new amphiphiles with a GPCR, we turned
to a human b2 adrenergic receptor-T4-lysozyme fusion pro-
tein (b2AR-T4L).[18] Stability was assessed through optical
absorption measurements of b2AR-T4L bound to the in-
verse agonist carazolol. b2AR-T4L was initially solubilized
and purified in DDM, and this detergent was then ex-
changed for the agent to be evaluated. The fluorescence
emission maximum of carazolol occurs at 356 nm in aqueous
solution, but emission is shifted to 341 nm in the receptor-
bound state. The 341:356 nm peak intensity ratio was used
to monitor the relative amounts of intact and denatured
b2AR-T4L, with Tm defined as the temperature at which the
341:356 nm peak intensity ratio is halfway between that of
fully native receptor and the fully denatured receptor. Fig-
ure 4a shows how Tm varies as a function of amphiphile con-
centration. At relatively low concentrations (<CMC+
0.05 wt%), DDM was superior to the new amphiphiles.
However, GLC-2 and GDN were superior to DDM at
higher concentrations.
Because GDN displayed particularly favorable behavior
in the preceding studies, this agent was further characterized
with Salmonella typhimurium melibiose permease (MelB)
expressed in E. coli.[20] DDM or GDN (1.5 wt%) was used
to extract MelB from E. coli membranes at 08C for 10 or
90 min and the aggregated material was removed by using
ultracentrifugation. The amount of MelB in solution was de-
termined by SDS-PAGE with immunoblot detection
(Figure 5). DDM could quantitatively extract MelB under
these conditions; GDN was not quite as efficient in extrac-
Figure 4. a) Melting temperatures (Tm) of b2AR-T4L, and b) b2AR WT
activity as a function of time, for proteins solubilized with new amphi-
philes or DDM. Tm values for b2AR-T4L are plotted in terms of wt% of
the amphiphile. b2AR WT was extracted with 1 wt% or 2 wt% amphi-
Figure 5. SDS-12% PAGE and Western blot analysis of MelB. Samples
were analyzed by SDS-PAGE analysis, and MelB was detected using
anti-histidine tag antibody. Each sample contained 10 mg protein. For ex-
tracts generated with each detergent or amphiphile at each temperature,
one sample was subjected to ultracentrifugation (+), and a comparison
sample was not (À). As a control, an untreated membrane sample
(“Memb.”; no ultracentrifugation) was included in each gel.
phile, and activity was measured periodically by radioACTHNUTRGENNUlG iACHTUTGNRENNUGgand-binding
assay using the antagonist [3H]-dihydroalprenolol. The solubilized b2AR
WT samples were stored at 48C.
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tion, although a substantial yield of MelB was obtained. We
assessed the effect of DDM and GDN on MelB thermosta-
bility by solubilizing the protein at elevated temperatures
for 90 min. DDM gave a high yield of soluble MelB at
458C, but at 558C no soluble protein was obtained; presum-
ably MelB denatured and aggregated at the higher tempera-
ture in the presence of DDM. In contrast, GDN provided
large amounts of soluble protein at 558C and even at 658C.
Interestingly, GDN could quantitatively extract the protein
at elevated temperatures. This result raises the possibility
that GDN may be more useful for extracting membrane
proteins at high temperatures relative to low temperatures
(e.g., 48C or 258C). When we used MelB of E. coli, similar
results were obtained (see the Supporting Information, Fig-
ure S6).
The favorable MelB extraction performance of GDN led
us to examine this amphiphile for extraction of other IMPs.
Comparable results were obtained when the LHI-RC super-
assembly was extracted from R. capsulatus membranes with
either 2 wt% GDN or 1 wt% DDM (GDN molecular
weight is more than twice that of DDM; see the Supporting
Information, Figure S7). For b2AR WT extraction from
insect cell membranes, 1 or 2 wt% GDN was more effective
than 1 wt% DDM; only a very small amount of b2AR WT
was detected with 1 wt% OG (Figure S7). DDM and GDN
were used to extract a CMP-Sia fusion protein bearing
green fluorescent protein (GFP) at the C-terminus, after ex-
pression in S. cerevisiae. The amount of solubilized protein
was estimated by total fluorescence. GDN (2 wt%), DDM
(1 wt%) and OG (1 wt%) gave approximately 70, 80 and
50% extraction yields, respectively. Overall, results with sev-
eral systems show that GDN is generally very effective at
extracting embedded proteins from biological membranes.
The results reported here suggest that GDN could prove
to be a useful tool for membrane protein research. Promis-
ing behavior has been observed for GLC amphiphiles as
well, in some cases. It is particularly noteworthy that our
tests have included membrane protein systems that vary in
terms of structure and function. These studies have included
systems that display only limited stability when solubilized
with conventional detergents, such as the R. capsulatus pho-
tosynthetic superassembly, LeuT, MelB, two forms of b2AR,
and dOR-T4L. DDM is probably the most popular conven-
tional detergent for IMP manipulations, and we have shown
that GDN consistently matches or exceeds DDM in terms
of both extracting and stabilizing diverse membrane pro-
teins.
(and perhaps complementary) advantages among the large
set of membrane proteins that have yet to be tamed in the
laboratory. The current work did not include comparative
studies with amphipols or nanodiscs, both of which have
proven to be excellent for stabilization of many membrane
protein systems, because neither of these types of agent is
likely to be useful for extraction of intrinsic membrane pro-
teins from lipid bilayers.
Typical detergents such as DDM, OG, and lauryldimethyl-
amine-N-oxide (LDAO) have simple alkyl chains as the lip-
ophilic groups. In the presence of a membrane protein,
these amphiphiles associate with one another to cover the
hydrophobic surfaces of the protein, resulting in protein–de-
tergent complexes (PDCs).[5m,21] The overall architectures of
the amphiphiles introduced here are similar to those of clas-
sical detergents in that the new compounds are neither fa-
cially amphiphilic nor polymeric. Consequently, the new
agents are anticipated to associate with membrane protein
in a similar way to classical detergents. Since, however, the
lipophilic groups of our new steroid-derived amphiphiles are
rigid and flat, we anticipate that these molecules will display
a stronger tendency to associate with complementary pro-
tein surfaces than do conventional detergents, and we pro-
pose that this tendency underlies the favorable solubilization
and stabilization properties we have demonstrated here.
Cholesterol and its derivatives are known to stabilize the
oxytocin receptor and b2AR through direct protein–choles-
terol interactions.[22] Because GDN, GLCs, and cholesterol
contain similar steroidal moieties, the new amphiphiles
could mimic these interactions of cholesterol with mem-
brane proteins.
Important questions remain to be addressed regarding the
precise roles of the steroidal units of the new amphiphiles.
However, even before these issues are explored, the poten-
tial promise of the new amphiphiles as tools for membrane-
protein manipulation is evident from their success with the
range of systems discussed above.
Acknowledgements
This work was supported by NIH grant P01 GM75913 (S.H.G.), NS28471
(B.K.), the European Communityꢁs Seventh Framework Programme FP7/
2007–2013 under grant agreement number HEALTH-F4–2007–201924,
EDICT Consortium (B.B., K.G., U.G.), the Danish National Research
Council (C.J. L., U.G.), the Lundbeck Foundation (S.G.F.R., C.J. L.,
U.G.), the National Research Foundation of Korea (NRF) funded by the
Ministry of Education, Science and Technology (grant number 2008–
0061856 to P.S.C., K.H.C.), and NIH grants R01 GM95538 and R21
HL087895 (to L.G.). R.R. was funded by the Defence, Science and Tech-
nology Laboratories (DSTL), Porton Down, UK. We thank Philip Laible
(Argonne National Laboratory) and, Elodie Point and Jean-Luc Popot
(Universitꢂ Paris-7) for supplying membrane preparations from R. capsu-
latus and purple membrane, respectively. We also thank Chiara Lee and
David Drew (Imperial College London) and, Jonathan Ruprecht (Medi-
cal Research Council-Mitochondrial Biology Unit, Cambridge) and Gary
Cecchini (University of California, San Francisco) for providing purified
GlpG and SQR samples, respectively.
We recently introduced the MNG amphiphile series,[5l]
molecules that are structurally quite different from GDN;
MNG amphiphiles have already proven their worth by ena-
bling the acquisition of new GPCR crystal structures.[6] The
present report includes a direct comparison of a new steroi-
dal agent GDN with MNG-3, which suggests that GDN
could be generally useful as a new tool for membrane pro-
tein solubilization and stabilization. Since the molecular
structures of MNG and GDN are very different, it is possi-
ble that these two types of amphiphile will manifest distinct
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P. S. Chae, L. Guan, C. J. Loland, B. Byrne, B. K. Kobilka, S. H. Gellman et al.
Thian, P. S. Chae, E. Pardon, D. Calinski, J. M. Mathiesen, S. T. A.
Keywords: amphiphiles · membrane proteins · molecular
design · solubilization · stabilization
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Received: January 8, 2012
Published online: && &&, 2012
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6
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www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

A New Class of Amphiphiles
COMMUNICATION
Amphiphiles
P. S. Chae,* S. G. F. Rasmussen,
R. R. Rana, K. Gotfryd, A. C. Kruse,
A. Manglik, K. H. Cho, S. Nurva,
U. Gether, L. Guan,* C. J. Loland,*
B. Byrne,* B. K. Kobilka,*
Non-traditional amphiphiles: Confer-
ring aqueous solubility on membrane
proteins generally requires the use of
a detergent or other amphiphilic agent.
A new class of amphiphiles was syn-
thesized, based on steroidal lipophilic
groups, and evaluated with several
membrane proteins. The results show
that the new amphiphile, “glyco-dio-
sgenin” (GDN; see figure), confers
enhanced stability to a variety of mem-
brane proteins in solution relative to
popular conventional detergents, such
as dodecylmaltoside (DDM).
S. H. Gellman* ............... &&&& — &&&&
A New Class of Amphiphiles Bearing
Rigid Hydrophobic Groups for Solubi-
lization and Stabilization of Membrane
Proteins
A class of structurally new amphiphiles based on steroidal lipophilic groups have
been prepared by P. S. Chae et al. on page && ff. The results show that the new
amphiphiles confer enhanced stability to a variety of membrane proteins in solution
relative to popular conventional detergent dodecylmaltoside (DDM). The potential
of the new amphiphiles as tools for solubilization, isolation, and stabilization is
evident from their success with a variety of membrane proteins.
Chem. Eur. J. 2012, 00, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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ÞÞ
These are not the final page numbers!