Biomedical Engineering Reference
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differences of the Raman intensity scattered from chiral molecules using right-
and left-circularly polarized incident laser light [10].
In this contribution we present the unique potential of the above-mentioned
Raman spectroscopic techniques for viral and microbial studies in biomedical
and pharmaceutical applications.
19.2 Viruses
Viruses are sub-microscopic non-cellular parasites without their own meta-
bolisms and therefore unable to grow or reproduce outside a host cell. Each
viral particle or virion consists of a nucleic acid molecule, single- or double-
stranded DNA, or single-stranded RNA. The nucleic acid molecule is encapsu-
lated with a protective protein coating, the so-called capsid, with a variety of
different shapes. The study of its geometry on a molecular level is of major im-
portance since it serves as a basis for morphological and antigenic distinction
and therefore for a structure-guided antiviral drug design [11].
19.2.1 Conventional Raman Spectroscopy
Conventional virus detection is based on a wide range of microbiological meth-
ods, like the detection of virus antigens, the analysis of antibodies as an im-
mune response (immunoblot, ELISA, or immunofluorescence), or the amplifi-
cation and detection of nucleic acid (polymerase chain reaction - PCR, in situ
hybridization). Recently X-ray crystallography and high-resolution nuclear
magnetic resonance (NMR) spectroscopy are also used for the analysis of the
molecular structure of viruses and biomolecules as well as their environment
and molecular interactions [12]. But these methods are often hampered due
to practical diculties [13]. Resent studies demonstrated that Raman spec-
troscopy is more widely applicable than these high-resolution methods since
there is no size limit or requirement for diffracting crystals [14]. It became ev-
ident that Raman spectroscopy is a promising method for a three-dimensional
structural analysis of viruses since Raman spectra of virus assemblies consist
of numerous Raman bands representing sensitive and selective molecular fin-
gerprints [15]. Raman investigations to elucidate virus assembly pathways, to
study the nucleic acid conformation and protein geometry of a wide variety of
viruses, RNA viruses, and single- and double-stranded DNA viruses as bacte-
riophages have been addressed. Tuma et al. studied conformational changes
in the coat protein subunit accompanied during the assembly of the procapsid
shell to a mature capsid of the bacteriophage P22, which is a prototype of the
morphogenesis of many double-stranded DNA viruses [16]. Another prototype
member of virulent bacteriophages is PRD1 consisting of an icosahedral cap-
sid that encloses a membrane-packaged double-stranded DNA genome. Other
Raman investigations focused on the characterization of changes in the P3
subunit structure and organization during shell capsid assembly of bacterio-
phage PRD1 [17].
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